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Performs left-to-right function composition for asynchronous functions.
Use Array.prototype.reduce() with the spread operator (...) to perform left-to-right function composition using Promise.then().
The functions can return a combination of: simple values, Promise's, or they can be defined as async ones returning through await.
All functions must be unary.
constsum=pipeAsyncFunctions(x=>x+1,x=>newPromise(resolve=>setTimeout(()=>resolve(x+2),1000)),x=>x+3,asyncx=>(awaitx)+4);(async()=>{console.log(awaitsum(5));// 15 (after one second)})();
Performs left-to-right function composition.
Use Array.prototype.reduce() with the spread operator (...) to perform left-to-right function composition.
The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.
⚠️NOTICE: The same functionality can be easily implemented by using the new asynchronous Clipboard API, which is still experimental but should be used in the future instead of this snippet. Find out more about it here.
Copy a string to the clipboard.
Only works as a result of user action (i.e. inside a click event listener).
Create a new <textarea> element, fill it with the supplied data and add it to the HTML document.
Use Selection.getRangeAt()to store the selected range (if any).
Use document.execCommand('copy') to copy to the clipboard.
Remove the <textarea> element from the HTML document.
Finally, use Selection().addRange() to recover the original selected range (if any).
copyToClipboard('Lorem ipsum');// 'Lorem ipsum' copied to clipboard.
Creates a counter with the specified range, step and duration for the specified selector.
Check if step has the proper sign and change it accordingly.
Use setInterval() in combination with Math.abs() and Math.floor() to calculate the time between each new text draw.
Use document.querySelector().innerHTML to update the value of the selected element.
Omit the fourth parameter, step, to use a default step of 1.
Omit the fifth parameter, duration, to use a default duration of 2000ms.
counter('#my-id',1,1000,5,2000);// Creates a 2-second timer for the element with id="my-id"
Creates an element from a string (without appending it to the document).
If the given string contains multiple elements, only the first one will be returned.
Use document.createElement() to create a new element.
Set its innerHTML to the string supplied as the argument.
Use ParentNode.firstElementChild to return the element version of the string.
Creates a pub/sub (publish–subscribe) event hub with emit, on, and off methods.
Use Object.create(null) to create an empty hub object that does not inherit properties from Object.prototype.
For emit, resolve the array of handlers based on the event argument and then run each one with Array.prototype.forEach() by passing in the data as an argument.
For on, create an array for the event if it does not yet exist, then use Array.prototype.push() to add the handler
to the array.
For off, use Array.prototype.findIndex() to find the index of the handler in the event array and remove it using Array.prototype.splice().
consthandler=data=>console.log(data);consthub=createEventHub();letincrement=0;// Subscribe: listen for different types of eventshub.on('message',handler);hub.on('message',()=>console.log('Message event fired'));hub.on('increment',()=>increment++);// Publish: emit events to invoke all handlers subscribed to them, passing the data to them as an argumenthub.emit('message','hello world');// logs 'hello world' and 'Message event fired'hub.emit('message',{hello: 'world'});// logs the object and 'Message event fired'hub.emit('increment');// `increment` variable is now 1// Unsubscribe: stop a specific handler from listening to the 'message' eventhub.off('message',handler);
Returns the current URL.
Use window.location.href to get current URL.
Code
constcurrentURL=()=>window.location.href;
Example
currentURL();// 'https://google.com'
Detects wether the website is being opened in a mobile device or a desktop/laptop.
Use a regular expression to test the navigator.userAgent property to figure out if the device is a mobile device or a desktop/laptop.
Returns true if the element specified is visible in the viewport, false otherwise.
Use Element.getBoundingClientRect() and the window.inner(Width|Height) values
to determine if a given element is visible in the viewport.
Omit the second argument to determine if the element is entirely visible, or specify true to determine if
it is partially visible.
// e.g. 100x100 viewport and a 10x10px element at position {top: -1, left: 0, bottom: 9, right: 10}elementIsVisibleInViewport(el);// false - (not fully visible)elementIsVisibleInViewport(el,true);// true - (partially visible)
Returns the scroll position of the current page.
Use pageXOffset and pageYOffset if they are defined, otherwise scrollLeft and scrollTop.
You can omit el to use a default value of window.
hide(document.querySelectorAll('img'));// Hides all <img> elements on the page
Redirects the page to HTTPS if its currently in HTTP. Also, pressing the back button doesn't take it back to the HTTP page as its replaced in the history.
Use location.protocol to get the protocol currently being used. If it's not HTTPS, use location.replace() to replace the existing page with the HTTPS version of the page. Use location.href to get the full address, split it with String.prototype.split() and remove the protocol part of the URL.
Returns true if the browser tab of the page is focused, false otherwise.
Use the Document.hidden property, introduced by the Page Visibility API to check if the browser tab of the page is visible or hidden.
Code
constisBrowserTabFocused=()=>!document.hidden;
Example
isBrowserTabFocused();// true
Converts a NodeList to an array.
Use spread operator inside new array to convert a NodeList to an array.
Code
constnodeListToArray=nodeList=>[...nodeList];
Example
nodeListToArray(document.childNodes);// [ <!DOCTYPE html>, html ]
Returns a new MutationObserver and runs the provided callback for each mutation on the specified element.
Use a MutationObserver to observe mutations on the given element.
Use Array.prototype.forEach() to run the callback for each mutation that is observed.
Omit the third argument, options, to use the default options (all true).
constobs=observeMutations(document,console.log);// Logs all mutations that happen on the pageobs.disconnect();// Disconnects the observer and stops logging mutations on the page
Removes an event listener from an element.
Use EventTarget.removeEventListener() to remove an event listener from an element.
Omit the fourth argument opts to use false or specify it based on the options used when the event listener was added.
constfn=()=>console.log('!');document.body.addEventListener('click',fn);off(document.body,'click',fn);// no longer logs '!' upon clicking on the page
Adds an event listener to an element with the ability to use event delegation.
Use EventTarget.addEventListener() to add an event listener to an element. If there is a target property supplied to the options object, ensure the event target matches the target specified and then invoke the callback by supplying the correct this context.
Returns a reference to the custom delegator function, in order to be possible to use with off.
Omit opts to default to non-delegation behavior and event bubbling.
constfn=()=>console.log('!');on(document.body,'click',fn);// logs '!' upon clicking the bodyon(document.body,'click',fn,{target: 'p'});// logs '!' upon clicking a `p` element child of the bodyon(document.body,'click',fn,{options: true});// use capturing instead of bubbling
Run the callback whenever the user input type changes (mouse or touch). Useful for enabling/disabling code depending on the input device. This process is dynamic and works with hybrid devices (e.g. touchscreen laptops).
Use two event listeners. Assume mouse input initially and bind a touchstart event listener to the document.
On touchstart, add a mousemove event listener to listen for two consecutive mousemove events firing within 20ms, using performance.now().
Run the callback with the input type as an argument in either of these situations.
onUserInputChange(type=>{console.log('The user is now using',type,'as an input method.');});
Returns the prefixed version (if necessary) of a CSS property that the browser supports.
Use Array.prototype.findIndex() on an array of vendor prefix strings to test if document.body has one of them defined in its CSSStyleDeclaration object, otherwise return null.
Use String.prototype.charAt() and String.prototype.toUpperCase() to capitalize the property, which will be appended to the vendor prefix string.
prefix('appearance');// 'appearance' on a supported browser, otherwise 'webkitAppearance', 'mozAppearance', 'msAppearance' or 'oAppearance'
Invokes the provided callback on each animation frame.
Use recursion.
Provided that running is true, continue invoking window.requestAnimationFrame() which invokes the provided callback.
Return an object with two methods start and stop to allow manual control of the recording.
Omit the second argument, autoStart, to implicitly call start when the function is invoked.
constcb=()=>console.log('Animation frame fired');constrecorder=recordAnimationFrames(cb);// logs 'Animation frame fired' on each animation framerecorder.stop();// stops loggingrecorder.start();// starts againconstrecorder2=recordAnimationFrames(cb,false);// `start` needs to be explicitly called to begin recording frames
Redirects to a specified URL.
Use window.location.href or window.location.replace() to redirect to url.
Pass a second argument to simulate a link click (true - default) or an HTTP redirect (false).
Runs a function in a separate thread by using a Web Worker, allowing long running functions to not block the UI.
Create a new Worker using a Blob object URL, the contents of which should be the stringified version of the supplied function.
Immediately post the return value of calling the function back.
Return a promise, listening for onmessage and onerror events and resolving the data posted back from the worker, or throwing an error.
Code
construnAsync=fn=>{constworker=newWorker(URL.createObjectURL(newBlob([`postMessage((${fn})());`]),{type: 'application/javascript; charset=utf-8'}));returnnewPromise((res,rej)=>{worker.onmessage=({ data })=>{res(data),worker.terminate();};worker.onerror=err=>{rej(err),worker.terminate();};});};
Example
constlongRunningFunction=()=>{letresult=0;for(leti=0;i<1000;i++){for(letj=0;j<700;j++){for(letk=0;k<300;k++){result=result+i+j+k;}}}returnresult;};/* NOTE: Since the function is running in a different context, closures are not supported. The function supplied to `runAsync` gets stringified, so everything becomes literal. All variables and functions must be defined inside.*/runAsync(longRunningFunction).then(console.log);// 209685000000runAsync(()=>10**3).then(console.log);// 1000letoutsideVariable=50;runAsync(()=>typeofoutsideVariable).then(console.log);// 'undefined'
Smooth-scrolls to the top of the page.
Get distance from top using document.documentElement.scrollTop or document.body.scrollTop.
Scroll by a fraction of the distance from the top. Use window.requestAnimationFrame() to animate the scrolling.
smoothScroll('#fooBar');// scrolls smoothly to the element with the id fooBarsmoothScroll('.fooBar');// scrolls smoothly to the first element with a class of fooBar
Toggle a class for an element.
Use element.classList.toggle() to toggle the specified class for the element.
toggleClass(document.querySelector('p.special'),'special');// The paragraph will not have the 'special' class anymore
Triggers a specific event on a given element, optionally passing custom data.
Use new CustomEvent() to create an event from the specified eventType and details.
Use el.dispatchEvent() to trigger the newly created event on the given element.
Omit the third argument, detail, if you do not want to pass custom data to the triggered event.
Use new Date() and Date.prototype.getFullYear() to get the first day of the year as a Date object, subtract it from the provided date and divide with the milliseconds in each day to get the result.
Use Math.floor() to appropriately round the resulting day count to an integer.
Returns the human readable format of the given number of milliseconds.
Divide ms with the appropriate values to obtain the appropriate values for day, hour, minute, second and millisecond.
Use Object.entries() with Array.prototype.filter() to keep only non-zero values.
Use Array.prototype.map() to create the string for each value, pluralizing appropriately.
Use String.prototype.join(', ') to combine the values into a string.
Results in a string representation of tomorrow's date.
Use new Date() to get today's date, adding one day using Date.getDate() and Date.setDate(), and converting the Date object to a string.
Code
consttomorrow=(long=false)=>{lett=newDate();t.setDate(t.getDate()+1);constret=`${t.getFullYear()}-${String(t.getMonth()+1).padStart(2,'0')}-${String(t.getDate()).padStart(2,'0')}`;return!long ? ret : `${ret}T00:00:00`;};
Example
tomorrow();// 2017-12-27 (if current date is 2017-12-26)tomorrow(true);// 2017-12-27T00:00:00 (if current date is 2017-12-26)
Attempts to invoke a function with the provided arguments, returning either the result or the caught error object.
Use a try... catch block to return either the result of the function or an appropriate error.
Code
constattempt=(fn, ...args)=>{try{returnfn(...args);}catch(e){returneinstanceofError ? e : newError(e);}};
Example
varelements=attempt(function(selector){returndocument.querySelectorAll(selector);},'>_>');if(elementsinstanceofError)elements=[];// elements = []
Creates a function that invokes fn with a given context, optionally adding any additional supplied parameters to the beginning of the arguments.
Return a function that uses Function.prototype.apply() to apply the given context to fn.
Use Array.prototype.concat() to prepend any additional supplied parameters to the arguments.
Creates a function that invokes the method at a given key of an object, optionally adding any additional supplied parameters to the beginning of the arguments.
Return a function that uses Function.prototype.apply() to bind context[fn] to context.
Use the spread operator (...) to prepend any additional supplied parameters to the arguments.
Use Array.prototype.reduce() to perform right-to-left function composition.
The last (rightmost) function can accept one or more arguments; the remaining functions must be unary.
Use Array.prototype.reduce() to perform left-to-right function composition.
The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.
Accepts a converging function and a list of branching functions and returns a function that applies each branching function to the arguments and the results of the branching functions are passed as arguments to the converging function.
Use Array.prototype.map() and Function.prototype.apply() to apply each function to the given arguments.
Use the spread operator (...) to call coverger with the results of all other functions.
Use recursion.
If the number of provided arguments (args) is sufficient, call the passed function fn.
Otherwise, return a curried function fn that expects the rest of the arguments.
If you want to curry a function that accepts a variable number of arguments (a variadic function, e.g. Math.min()), you can optionally pass the number of arguments to the second parameter arity.
Creates a debounced function that delays invoking the provided function until at least ms milliseconds have elapsed since the last time it was invoked.
Each time the debounced function is invoked, clear the current pending timeout with clearTimeout() and use setTimeout() to create a new timeout that delays invoking the function until at least ms milliseconds has elapsed. Use Function.prototype.apply() to apply the this context to the function and provide the necessary arguments.
Omit the second argument, ms, to set the timeout at a default of 0 ms.
window.addEventListener('resize',debounce(()=>{console.log(window.innerWidth);console.log(window.innerHeight);},250));// Will log the window dimensions at most every 250ms
Defers invoking a function until the current call stack has cleared.
Use setTimeout() with a timeout of 1ms to add a new event to the browser event queue and allow the rendering engine to complete its work. Use the spread (...) operator to supply the function with an arbitrary number of arguments.
// Example A:defer(console.log,'a'),console.log('b');// logs 'b' then 'a'// Example B:document.querySelector('#someElement').innerHTML='Hello';longRunningFunction();//Browser will not update the HTML until this has finisheddefer(longRunningFunction);// Browser will update the HTML then run the function
Invokes the provided function after wait milliseconds.
Use setTimeout() to delay execution of fn.
Use the spread (...) operator to supply the function with an arbitrary number of arguments.
functionName(Math.max);// max (logged in debug channel of console)
Returns the number of times a function executed per second.
hz is the unit for hertz, the unit of frequency defined as one cycle per second.
Use performance.now() to get the difference in milliseconds before and after the iteration loop to calculate the time elapsed executing the function iterations times.
Return the number of cycles per second by converting milliseconds to seconds and dividing it by the time elapsed.
Omit the second argument, iterations, to use the default of 100 iterations.
// 10,000 element arrayconstnumbers=Array(10000).fill().map((_,i)=>i);// Test functions with the same goal: sum up the elements in the arrayconstsumReduce=()=>numbers.reduce((acc,n)=>acc+n,0);constsumForLoop=()=>{letsum=0;for(leti=0;i<numbers.length;i++)sum+=numbers[i];returnsum;};// `sumForLoop` is nearly 10 times fasterMath.round(hz(sumReduce));// 572Math.round(hz(sumForLoop));// 4784
Returns the memoized (cached) function.
Create an empty cache by instantiating a new Map object.
Return a function which takes a single argument to be supplied to the memoized function by first checking if the function's output for that specific input value is already cached, or store and return it if not. The function keyword must be used in order to allow the memoized function to have its this context changed if necessary.
Allow access to the cache by setting it as a property on the returned function.
// See the `anagrams` snippet.constanagramsCached=memoize(anagrams);anagramsCached('javascript');// takes a long timeanagramsCached('javascript');// returns virtually instantly since it's now cachedconsole.log(anagramsCached.cache);// The cached anagrams map
Negates a predicate function.
Take a predicate function and apply the not operator (!) to it with its arguments.
Utilizing a closure, use a flag, called, and set it to true once the function is called for the first time, preventing it from being called again. In order to allow the function to have its this context changed (such as in an event listener), the function keyword must be used, and the supplied function must have the context applied.
Allow the function to be supplied with an arbitrary number of arguments using the rest/spread (...) operator.
conststartApp=function(event){console.log(this,event);// document.body, MouseEvent};document.body.addEventListener('click',once(startApp));// only runs `startApp` once upon click
Creates a function that invokes fn with partials prepended to the arguments it receives.
Use the spread operator (...) to prepend partials to the list of arguments of fn.
constdelay=d=>newPromise(r=>setTimeout(r,d));runPromisesInSeries([()=>delay(1000),()=>delay(2000)]);// Executes each promise sequentially, taking a total of 3 seconds to complete
Delays the execution of an asynchronous function.
Delay executing part of an async function, by putting it to sleep, returning a Promise.
asyncfunctionsleepyWork(){console.log("I'm going to sleep for 1 second.");awaitsleep(1000);console.log('I woke up after 1 second.');}
Creates a throttled function that only invokes the provided function at most once per every wait milliseconds
Use setTimeout() and clearTimeout() to throttle the given method, fn.
Use Function.prototype.apply() to apply the this context to the function and provide the necessary arguments.
Use Date.now() to keep track of the last time the throttled function was invoked.
Omit the second argument, wait, to set the timeout at a default of 0 ms.
window.addEventListener('resize',throttle(function(evt){console.log(window.innerWidth);console.log(window.innerHeight);},250));// Will log the window dimensions at most every 250ms
Iterates over a callback n times
Use Function.call() to call fnn times or until it returns false.
Omit the last argument, context, to use an undefined object (or the global object in non-strict mode).
Return a variadic function.
Use Array.prototype.reduce() on the provided arguments to call each subsequent curry level of the function.
If the length of the provided arguments is less than n throw an error.
Otherwise, call fn with the proper amount of arguments, using Array.prototype.slice(0, n).
Omit the second argument, n, to uncurry up to depth 1.
Code
constuncurry=(fn,n=1)=>(...args)=>{constnext=acc=>args=>args.reduce((x,y)=>x(y),acc);if(n>args.length)thrownewRangeError('Arguments too few!');returnnext(fn)(args.slice(0,n));};
Builds an array, using an iterator function and an initial seed value.
Use a while loop and Array.prototype.push() to call the function repeatedly until it returns false.
The iterator function accepts one argument (seed) and must always return an array with two elements ([value, nextSeed]) or false to terminate.
Returns the average of an array, after mapping each element to a value using the provided function.
Use Array.prototype.map() to map each element to the value returned by fn, Array.prototype.reduce() to add each value to an accumulator, initialized with a value of 0, divide by the length of the array.
Evaluates the binomial coefficient of two integers n and k.
Use Number.isNaN() to check if any of the two values is NaN.
Check if k is less than 0, greater than or equal to n, equal to 1 or n - 1 and return the appropriate result.
Check if n - k is less than k and switch their values accordingly.
Loop from 2 through k and calculate the binomial coefficient.
Use Math.round() to account for rounding errors in the calculation.
Use Math.PI and the degree to radian formula to convert the angle from degrees to radians.
Code
constdegreesToRads=deg=>(deg*Math.PI)/180.0;
Example
degreesToRads(90.0);// ~1.5708
Converts a number to an array of digits.
Convert the number to a string, using the spread operator (...) to build an array.
Use Array.prototype.map() and parseInt() to transform each value to an integer.
Code
constdigitize=n=>[...`${n}`].map(i=>parseInt(i));
Example
digitize(123);// [1, 2, 3]
Returns the distance between two points.
Use Math.hypot() to calculate the Euclidean distance between two points.
Computes the new ratings between two or more opponents using the Elo rating system. It takes an array
of pre-ratings and returns an array containing post-ratings.
The array should be ordered from best performer to worst performer (winner -> loser).
Use the exponent ** operator and math operators to compute the expected score (chance of winning).
of each opponent and compute the new rating for each.
Loop through the ratings, using each permutation to compute the post-Elo rating for each player in a pairwise fashion.
Omit the second argument to use the default kFactor of 32.
Code
constelo=([...ratings],kFactor=32,selfRating)=>{const[a,b]=ratings;constexpectedScore=(self,opponent)=>1/(1+10**((opponent-self)/400));constnewRating=(rating,i)=>(selfRating||rating)+kFactor*(i-expectedScore(i ? a : b,i ? b : a));if(ratings.length===2){return[newRating(a,1),newRating(b,0)];}for(leti=0,len=ratings.length;i<len;i++){letj=i;while(j<len-1){j++;[ratings[i],ratings[j]]=elo([ratings[i],ratings[j]],kFactor);}}returnratings;};
Example
// Standard 1v1selo([1200,1200]);// [1216, 1184]elo([1200,1200],64);// [1232, 1168]// 4 player FFA, all same rankelo([1200,1200,1200,1200]).map(Math.round);// [1246, 1215, 1185, 1154]/*For teams, each rating can adjusted based on own team's average rating vs.average rating of opposing team, with the score being added to theirown individual rating by supplying it as the third argument.*/
Calculates the factorial of a number.
Use recursion.
If n is less than or equal to 1, return 1.
Otherwise, return the product of n and the factorial of n - 1.
Throws an exception if n is a negative number.
Code
constfactorial=n=>n<0
? (()=>{thrownewTypeError('Negative numbers are not allowed!');})()
: n<=1
? 1
: n*factorial(n-1);
Example
factorial(6);// 720
Generates an array, containing the Fibonacci sequence, up until the nth term.
Create an empty array of the specific length, initializing the first two values (0 and 1).
Use Array.prototype.reduce() to add values into the array, using the sum of the last two values, except for the first two.
Calculates the greatest common divisor between two or more numbers/arrays.
The inner _gcd function uses recursion.
Base case is when y equals 0. In this case, return x.
Otherwise, return the GCD of y and the remainder of the division x/y.
Code
constgcd=(...arr)=>{const_gcd=(x,y)=>(!y ? x : gcd(y,x%y));return[...arr].reduce((a,b)=>_gcd(a,b));};
Example
gcd(8,36);// 4gcd(...[12,8,32]);// 4
Initializes an array containing the numbers in the specified range where start and end are inclusive and the ratio between two terms is step.
Returns an error if step equals 1.
Use Array.from(), Math.log() and Math.floor() to create an array of the desired length, Array.prototype.map() to fill with the desired values in a range.
Omit the second argument, start, to use a default value of 1.
Omit the third argument, step, to use a default value of 2.
Calculates the Hamming distance between two values.
Use XOR operator (^) to find the bit difference between the two numbers, convert to a binary string using toString(2).
Count and return the number of 1s in the string, using match(/1/g).
Checks if the given number falls within the given range.
Use arithmetic comparison to check if the given number is in the specified range.
If the second parameter, end, is not specified, the range is considered to be from 0 to start.
Returns true if the given number is even, false otherwise.
Checks whether a number is odd or even using the modulo (%) operator.
Returns true if the number is even, false if the number is odd.
Code
constisEven=num=>num%2===0;
Example
isEven(3);// false
Checks if the provided integer is a prime number.
Check numbers from 2 to the square root of the given number.
Return false if any of them divides the given number, else return true, unless the number is less than 2.
Returns the least common multiple of two or more numbers.
Use the greatest common divisor (GCD) formula and the fact that lcm(x,y) = x * y / gcd(x,y) to determine the least common multiple.
The GCD formula uses recursion.
Code
constlcm=(...arr)=>{constgcd=(x,y)=>(!y ? x : gcd(y,x%y));const_lcm=(x,y)=>(x*y)/gcd(x,y);return[...arr].reduce((a,b)=>_lcm(a,b));};
Example
lcm(12,7);// 84lcm(...[1,3,4,5]);// 60
Implementation of the Luhn Algorithm used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers etc.
Use String.prototype.split(''), Array.prototype.reverse() and Array.prototype.map() in combination with parseInt() to obtain an array of digits.
Use Array.prototype.splice(0,1) to obtain the last digit.
Use Array.prototype.reduce() to implement the Luhn Algorithm.
Return true if sum is divisible by 10, false otherwise.
Find the middle of the array, use Array.prototype.sort() to sort the values.
Return the number at the midpoint if length is odd, otherwise the average of the two middle numbers.
Generates primes up to a given number, using the Sieve of Eratosthenes.
Generate an array from 2 to the given number. Use Array.prototype.filter() to filter out the values divisible by any number from 2 to the square root of the provided number.
Use Math.PI and the radian to degree formula to convert the angle from radians to degrees.
Code
constradsToDegrees=rad=>(rad*180.0)/Math.PI;
Example
radsToDegrees(Math.PI/2);// 90
Returns an array of n random integers in the specified range.
Use Array.from() to create an empty array of the specific length, Math.random() to generate a random number and map it to the desired range, using Math.floor() to make it an integer.
Use Math.round() and template literals to round the number to the specified number of digits.
Omit the second argument, decimals to round to an integer.
Returns the standard deviation of an array of numbers.
Use Array.prototype.reduce() to calculate the mean, variance and the sum of the variance of the values, the variance of the values, then
determine the standard deviation.
You can omit the second argument to get the sample standard deviation or set it to true to get the population standard deviation.
Returns the sum of an array, after mapping each element to a value using the provided function.
Use Array.prototype.map() to map each element to the value returned by fn, Array.prototype.reduce() to add each value to an accumulator, initialized with a value of 0.
Returns the sum of the powers of all the numbers from start to end (both inclusive).
Use Array.prototype.fill() to create an array of all the numbers in the target range, Array.prototype.map() and the exponent operator (**) to raise them to power and Array.prototype.reduce() to add them together.
Omit the second argument, power, to use a default power of 2.
Omit the third argument, start, to use a default starting value of 1.
Add special characters to text to print in color in the console (combined with console.log()).
Use template literals and special characters to add the appropriate color code to the string output.
For background colors, add a special character that resets the background color at the end of the string.
console.log(colorize('foo').red);// 'foo' (red letters)console.log(colorize('foo','bar').bgBlue);// 'foo bar' (blue background)console.log(colorize(colorize('foo').yellow,colorize('foo').green).bgWhite);// 'foo bar' (first word in yellow letters, second word in green letters, white background for both)
Check if the current process's arguments contain the specified flags.
Use Array.prototype.every() and Array.prototype.includes() to check if process.argv contains all the specified flags.
Use a regular expression to test if the specified flags are prefixed with - or -- and prefix them accordingly.
Code
consthasFlags=(...flags)=>flags.every(flag=>process.argv.includes(/^-{1,2}/.test(flag) ? flag : '--'+flag));
JSONToFile({test: 'is passed'},'testJsonFile');// writes the object to 'testJsonFile.json'
Returns an array of lines from the specified file.
Use readFileSync function in fs node package to create a Buffer from a file.
convert buffer to string using toString(encoding) function.
creating an array from contents of file by spliting file content line by line (each \n).
Binds methods of an object to the object itself, overwriting the existing method.
Use Array.prototype.forEach() to return a function that uses Function.prototype.apply() to apply the given context (obj) to fn for each function specified.
varview={label: 'docs',click: function(){console.log('clicked '+this.label);}};bindAll(view,'click');jQuery(element).on('click',view.click);// Logs 'clicked docs' when clicked.
Creates a deep clone of an object.
Use recursion.
Use Object.assign() and an empty object ({}) to create a shallow clone of the original.
Use Object.keys() and Array.prototype.forEach() to determine which key-value pairs need to be deep cloned.
'use strict';consto=deepFreeze([1,[2,3]]);o[0]=3;// not allowedo[1][0]=4;// not allowed as well
Assigns default values for all properties in an object that are undefined.
Use Object.assign() to create a new empty object and copy the original one to maintain key order, use Array.prototype.reverse() and the spread operator ... to combine the default values from left to right, finally use obj again to overwrite properties that originally had a value.
Returns the target value in a nested JSON object, based on the given key.
Use the in operator to check if target exists in obj.
If found, return the value of obj[target], otherwise use Object.values(obj) and Array.prototype.reduce() to recursively call dig on each nested object until the first matching key/value pair is found.
Performs a deep comparison between two values to determine if they are equivalent.
Check if the two values are identical, if they are both Date objects with the same time, using Date.getTime() or if they are both non-object values with an equivalent value (strict comparison).
Check if only one value is null or undefined or if their prototypes differ.
If none of the above conditions are met, use Object.keys() to check if both values have the same number of keys, then use Array.prototype.every() to check if every key in the first value exists in the second one and if they are equivalent by calling this method recursively.
Returns the first key that satisfies the provided testing function. Otherwise undefined is returned.
Use Object.keys(obj) to get all the properties of the object, Array.prototype.find() to test the provided function for each key-value pair. The callback receives three arguments - the value, the key and the object.
Returns the last key that satisfies the provided testing function.
Otherwise undefined is returned.
Use Object.keys(obj) to get all the properties of the object, Array.prototype.reverse() to reverse their order and Array.prototype.find() to test the provided function for each key-value pair.
The callback receives three arguments - the value, the key and the object.
Use recursion.
Use Object.keys(obj) combined with Array.prototype.reduce() to convert every leaf node to a flattened path node.
If the value of a key is an object, the function calls itself with the appropriate prefix to create the path using Object.assign().
Otherwise, it adds the appropriate prefixed key-value pair to the accumulator object.
You should always omit the second argument, prefix, unless you want every key to have a prefix.
Iterates over all own properties of an object, running a callback for each one.
Use Object.keys(obj) to get all the properties of the object, Array.prototype.forEach() to run the provided function for each key-value pair. The callback receives three arguments - the value, the key and the object.
Iterates over all own properties of an object in reverse, running a callback for each one.
Use Object.keys(obj) to get all the properties of the object, Array.prototype.reverse() to reverse their order and Array.prototype.forEach() to run the provided function for each key-value pair. The callback receives three arguments - the value, the key and the object.
Returns an array of function property names from own (and optionally inherited) enumerable properties of an object.
Use Object.keys(obj) to iterate over the object's own properties.
If inherited is true, use Object.get.PrototypeOf(obj) to also get the object's inherited properties.
Use Array.prototype.filter() to keep only those properties that are functions.
Omit the second argument, inherited, to not include inherited properties by default.
Retrieve a set of properties indicated by the given selectors from an object.
Use Array.prototype.map() for each selector, String.prototype.replace() to replace square brackets with dots, String.prototype.split('.') to split each selector, Array.prototype.filter() to remove empty values and Array.prototype.reduce() to get the value indicated by it.
constobj={selector: {to: {val: 'val to select'}},target: [1,2,{a: 'test'}]};get(obj,'selector.to.val','target[0]','target[2].a');// ['val to select', 1, 'test']
Inverts the key-value pairs of an object, without mutating it. The corresponding inverted value of each inverted key is an array of keys responsible for generating the inverted value. If a function is supplied, it is applied to each inverted key.
Use Object.keys() and Array.prototype.reduce() to invert the key-value pairs of an object and apply the function provided (if any).
Omit the second argument, fn, to get the inverted keys without applying a function to them.
Creates a new object from the specified object, where all the keys are in lowercase.
Use Object.keys() and Array.prototype.reduce() to create a new object from the specified object.
Convert each key in the original object to lowercase, using String.toLowerCase().
Creates an object with keys generated by running the provided function for each key and the same values as the provided object.
Use Object.keys(obj) to iterate over the object's keys.
Use Array.prototype.reduce() to create a new object with the same values and mapped keys using fn.
Creates an object with the same keys as the provided object and values generated by running the provided function for each value.
Use Object.keys(obj) to iterate over the object's keys.
Use Array.prototype.reduce() to create a new object with the same keys and mapped values using fn.
Compares two objects to determine if the first one contains equivalent property values to the second one.
Use Object.keys(source) to get all the keys of the second object, then Array.prototype.every(), Object.hasOwnProperty() and strict comparison to determine if all keys exist in the first object and have the same values.
Compares two objects to determine if the first one contains equivalent property values to the second one, based on a provided function.
Use Object.keys(source) to get all the keys of the second object, then Array.prototype.every(), Object.hasOwnProperty() and the provided function to determine if all keys exist in the first object and have equivalent values.
If no function is provided, the values will be compared using the equality operator.
Creates a new object from the combination of two or more objects.
Use Array.prototype.reduce() combined with Object.keys(obj) to iterate over all objects and keys.
Use hasOwnProperty() and Array.prototype.concat() to append values for keys existing in multiple objects.
Given a flat array of objects linked to one another, it will nest them recursively.
Useful for nesting comments, such as the ones on reddit.com.
Use recursion.
Use Array.prototype.filter() to filter the items where the id matches the link, then Array.prototype.map() to map each one to a new object that has a children property which recursively nests the items based on which ones are children of the current item.
Omit the second argument, id, to default to null which indicates the object is not linked to another one (i.e. it is a top level object).
Omit the third argument, link, to use 'parent_id' as the default property which links the object to another one by its id.
Omits the key-value pairs corresponding to the given keys from an object.
Use Object.keys(obj), Array.prototype.filter() and Array.prototype.includes() to remove the provided keys.
Use Array.prototype.reduce() to convert the filtered keys back to an object with the corresponding key-value pairs.
Creates an object composed of the properties the given function returns falsey for. The function is invoked with two arguments: (value, key).
Use Object.keys(obj) and Array.prototype.filter()to remove the keys for which fn returns a truthy value.
Use Array.prototype.reduce() to convert the filtered keys back to an object with the corresponding key-value pairs.
Returns a sorted array of objects ordered by properties and orders.
Uses Array.prototype.sort(), Array.prototype.reduce() on the props array with a default value of 0, use array destructuring to swap the properties position depending on the order passed.
If no orders array is passed it sort by 'asc' by default.
Picks the key-value pairs corresponding to the given keys from an object.
Use Array.prototype.reduce() to convert the filtered/picked keys back to an object with the corresponding key-value pairs if the key exists in the object.
Creates an object composed of the properties the given function returns truthy for. The function is invoked with two arguments: (value, key).
Use Object.keys(obj) and Array.prototype.filter()to remove the keys for which fn returns a falsey value.
Use Array.prototype.reduce() to convert the filtered keys back to an object with the corresponding key-value pairs.
Replaces the names of multiple object keys with the values provided.
Use Object.keys() in combination with Array.prototype.reduce() and the spread operator (...) to get the object's keys and rename them according to keysMap.
Use Object.assign() and an empty object ({}) to create a shallow clone of the original.
Code
constshallowClone=obj=>Object.assign({},obj);
Example
consta={x: true,y: 1};constb=shallowClone(a);// a !== b
Get size of arrays, objects or strings.
Get type of val (array, object or string).
Use length property for arrays.
Use length or size value if available or number of keys for objects.
Use size of a Blob object created from val for strings.
Split strings into array of characters with split('') and return its length.
Applies a function against an accumulator and each key in the object (from left to right).
Use Object.keys(obj) to iterate over each key in the object, Array.prototype.reduce() to call the apply the specified function against the given accumulator.
Use Object.keys(obj) combined with Array.prototype.reduce() to convert flattened path node to a leaf node.
If the value of a key contains a dot delimiter (.), use Array.prototype.split('.'), string transformations and JSON.parse() to create an object, then Object.assign() to create the leaf node.
Otherwise, add the appropriate key-value pair to the accumulator object.
Convert a given string to a Blob Object and find its size.
Code
constbyteSize=str=>newBlob([str]).size;
Example
byteSize('😀');// 4byteSize('Hello World');// 11
Capitalizes the first letter of a string.
Use array destructuring and String.prototype.toUpperCase() to capitalize first letter, ...rest to get array of characters after first letter and then Array.prototype.join('') to make it a string again.
Omit the lowerRest parameter to keep the rest of the string intact, or set it to true to convert to lowercase.
Converts a comma-separated values (CSV) string to a 2D array.
Use Array.prototype.slice() and Array.prototype.indexOf('\n') to remove the first row (title row) if omitFirstRow is true.
Use String.prototype.split('\n') to create a string for each row, then String.prototype.split(delimiter) to separate the values in each row.
Omit the second argument, delimiter, to use a default delimiter of ,.
Omit the third argument, omitFirstRow, to include the first row (title row) of the CSV string.
Converts a comma-separated values (CSV) string to a 2D array of objects.
The first row of the string is used as the title row.
Use Array.prototype.slice() and Array.prototype.indexOf('\n') and String.prototype.split(delimiter) to separate the first row (title row) into values.
Use String.prototype.split('\n') to create a string for each row, then Array.prototype.map() and String.prototype.split(delimiter) to separate the values in each row.
Use Array.prototype.reduce() to create an object for each row's values, with the keys parsed from the title row.
Omit the second argument, delimiter, to use a default delimiter of ,.
Use array destructuring and String.toLowerCase() to decapitalize first letter, ...rest to get array of characters after first letter and then Array.prototype.join('') to make it a string again.
Omit the upperRest parameter to keep the rest of the string intact, or set it to true to convert to uppercase.
Use String.prototype.replace() with a regexp that matches the characters that need to be escaped, using a callback function to replace each character instance with its associated escaped character using a dictionary (object).
Use String.prototype.replace() to remove underscores, hyphens, and spaces and convert words to camelcase.
Omit the second argument to use a default separator of _.
fromCamelCase('someDatabaseFieldName',' ');// 'some database field name'fromCamelCase('someLabelThatNeedsToBeCamelized','-');// 'some-label-that-needs-to-be-camelized'fromCamelCase('someJavascriptProperty','_');// 'some_javascript_property'
Indents each line in the provided string.
Use String.replace and a regular expression to add the character specified by indentcount times at the start of each line.
Omit the third parameter, indent, to use a default indentation character of ' '.
Checks if a string is an anagram of another string (case-insensitive, ignores spaces, punctuation and special characters).
Use String.toLowerCase(), String.prototype.replace() with an appropriate regular expression to remove unnecessary characters, String.prototype.split(''), Array.prototype.sort() and Array.prototype.join('') on both strings to normalize them, then check if their normalized forms are equal.
Creates a new string with the results of calling a provided function on every character in the calling string.
Use String.prototype.split('') and Array.prototype.map() to call the provided function, fn, for each character in str.
Use Array.prototype.join('') to recombine the array of characters into a string.
The callback function, fn, takes three arguments (the current character, the index of the current character and the string mapString was called upon).
Replaces all but the last num of characters with the specified mask character.
Use String.prototype.slice() to grab the portion of the characters that will remain unmasked and use String.padStart() to fill the beginning of the string with the mask character up to the original length.
Omit the second argument, num, to keep a default of 4 characters unmasked. If num is negative, the unmasked characters will be at the start of the string.
Omit the third argument, mask, to use a default character of '*' for the mask.
Pads a string on both sides with the specified character, if it's shorter than the specified length.
Use String.padStart() and String.padEnd() to pad both sides of the given string.
Omit the third argument, char, to use the whitespace character as the default padding character.
Returns true if the given string is a palindrome, false otherwise.
Convert string String.toLowerCase() and use String.prototype.replace() to remove non-alphanumeric characters from it.
Then, use the spread operator (...) to split string into individual characters, Array.prototype.reverse(), String.prototype.join('') and compare to the original, unreversed string, after converting it String.tolowerCase().
Returns the singular or plural form of the word based on the input number. If the first argument is an object, it will use a closure by returning a function that can auto-pluralize words that don't simply end in s if the supplied dictionary contains the word.
If num is either -1 or 1, return the singular form of the word. If num is any other number, return the plural form. Omit the third argument to use the default of the singular word + s, or supply a custom pluralized word when necessary. If the first argument is an object, utilize a closure by returning a function which can use the supplied dictionary to resolve the correct plural form of the word.
Code
constpluralize=(val,word,plural=word+'s')=>{const_pluralize=(num,word,plural=word+'s')=>[1,-1].includes(Number(num)) ? word : plural;if(typeofval==='object')return(num,word)=>_pluralize(num,word,val[word]);return_pluralize(val,word,plural);};
Use the spread operator (...) and Array.prototype.reverse() to reverse the order of the characters in the string.
Combine characters to get a string using String.prototype.join('').
Use the spread operator (...), Array.prototype.sort() and String.localeCompare() to sort the characters in str, recombine using String.prototype.join('').
⚠️WARNING: This function's execution time increases exponentially with each character. Anything more than 8 to 10 characters will cause your browser to hang as it tries to solve all the different combinations.
Generates all permutations of a string (contains duplicates).
Use recursion.
For each letter in the given string, create all the partial permutations for the rest of its letters.
Use Array.prototype.map() to combine the letter with each partial permutation, then Array.prototype.reduce() to combine all permutations in one array.
Base cases are for string length equal to 2 or 1.
toCamelCase('some_database_field_name');// 'someDatabaseFieldName'toCamelCase('Some label that needs to be camelized');// 'someLabelThatNeedsToBeCamelized'toCamelCase('some-javascript-property');// 'someJavascriptProperty'toCamelCase('some-mixed_string with spaces_underscores-and-hyphens');// 'someMixedStringWithSpacesUnderscoresAndHyphens'
Converts a string to kebab case.
Break the string into words and combine them adding - as a separator, using a regexp.
toSnakeCase('camelCase');// 'camel_case'toSnakeCase('some text');// 'some_text'toSnakeCase('some-mixed_string With spaces_underscores-and-hyphens');// 'some_mixed_string_with_spaces_underscores_and_hyphens'toSnakeCase('AllThe-small Things');// "all_the_smal_things"toSnakeCase('IAmListeningToFMWhileLoadingDifferentURLOnMyBrowserAndAlsoEditingSomeXMLAndHTML');// "i_am_listening_to_fm_while_loading_different_url_on_my_browser_and_also_editing_some_xml_and_html"
Truncates a string up to a specified length.
Determine if the string's length is greater than num.
Return the string truncated to the desired length, with '...' appended to the end or the original string.
Use String.prototype.replace() with a regex that matches the characters that need to be unescaped, using a callback function to replace each escaped character instance with its associated unescaped character using a dictionary (object).
unescapeHTML('<a href="#">Me & you</a>');// '<a href="#">Me & you</a>'
Joins all given URL segments together, then normalizes the resulting URL.
Use String.prototype.join('/') to combine URL segments, then a series of String.prototype.replace() calls with various regexps to normalize the resulting URL (remove double slashes, add proper slashes for protocol, remove slashes before parameters, combine parameters with '&' and normalize first parameter delimiter).
Use String.prototype.split() with a supplied pattern (defaults to non-alpha as a regexp) to convert to an array of strings. Use Array.prototype.filter() to remove any empty strings.
Omit the second argument to use the default regexp.
Checks if the provided value is of the specified type.
Ensure the value is not undefined or null using Array.prototype.includes(), and compare the constructor property on the value with type to check if the provided value is of the specified type.
Checks if the given argument is a native boolean element.
Use typeof to check if a value is classified as a boolean primitive.
Code
constisBoolean=val=>typeofval==='boolean';
Example
isBoolean(null);// falseisBoolean(false);// true
Returns true if the a value is an empty object, collection, map or set, has no enumerable properties or is any type that is not considered a collection.
Check if the provided value is null or if its length is equal to 0.
isEmpty(newMap());// trueisEmpty(newSet());// trueisEmpty([]);// trueisEmpty({});// trueisEmpty('');// trueisEmpty([1,2]);// falseisEmpty({a: 1,b: 2});// falseisEmpty('text');// falseisEmpty(123);// true - type is not considered a collectionisEmpty(true);// true - type is not considered a collection
Checks if the given argument is a function.
Use typeof to check if a value is classified as a function primitive.
Code
constisFunction=val=>typeofval==='function';
Example
isFunction('x');// falseisFunction(x=>x);// true
Returns true if the specified value is null or undefined, false otherwise.
Use the strict equality operator to check if the value and of val are equal to null or undefined.
Code
constisNil=val=>val===undefined||val===null;
Example
isNil(null);// trueisNil(undefined);// true
Returns true if the specified value is null, false otherwise.
Use the strict equality operator to check if the value and of val are equal to null.
Code
constisNull=val=>val===null;
Example
isNull(null);// true
Checks if the given argument is a number.
Use typeof to check if a value is classified as a number primitive.
Code
constisNumber=val=>typeofval==='number';
Example
isNumber('1');// falseisNumber(1);// true
Returns a boolean determining if the passed value is an object or not.
Uses the Object constructor to create an object wrapper for the given value.
If the value is null or undefined, create and return an empty object. Οtherwise, return an object of a type that corresponds to the given value.
Returns a boolean determining if the passed value is primitive or not.
Use Array.prototype.includes() on an array of type strings which are not primitive,
supplying the type using typeof.
Since typeof null evaluates to 'object', it needs to be directly compared.
Extends a 3-digit color code to a 6-digit color code.
Use Array.prototype.map(), String.prototype.split() and Array.prototype.join() to join the mapped array for converting a 3-digit RGB notated hexadecimal color-code to the 6-digit form.
Array.prototype.slice() is used to remove # from string start since it's added once.
Returns an object containing the parameters of the current URL.
Use String.match() with an appropriate regular expression to get all key-value pairs, Array.prototype.reduce() to map and combine them into a single object.
Pass location.search as the argument to apply to the current url.
Converts a color code to a rgb() or rgba() string if alpha value is provided.
Use bitwise right-shift operator and mask bits with & (and) operator to convert a hexadecimal color code (with or without prefixed with #) to a string with the RGB values. If it's 3-digit color code, first convert to 6-digit version. If an alpha value is provided alongside 6-digit hex, give rgba() string in return.
Use XMLHttpRequest web api to make a get request to the given url.
Handle the onload event, by calling the given callback the responseText.
Handle the onerror event, by running the provided err function.
Omit the third argument, err, to log errors to the console's error stream by default.
httpGet('https://jsonplaceholder.typicode.com/posts/1',console.log);/* Logs: { "userId": 1, "id": 1, "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", "body": "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto"}*/
Makes a POST request to the passed URL.
Use XMLHttpRequest web api to make a post request to the given url.
Set the value of an HTTP request header with setRequestHeader method.
Handle the onload event, by calling the given callback the responseText.
Handle the onerror event, by running the provided err function.
Omit the third argument, data, to send no data to the provided url.
Omit the fourth argument, err, to log errors to the console's error stream by default.
constnewPost={userId: 1,id: 1337,title: 'Foo',body: 'bar bar bar'};constdata=JSON.stringify(newPost);httpPost('https://jsonplaceholder.typicode.com/posts',data,console.log);/*Logs: { "userId": 1, "id": 1337, "title": "Foo", "body": "bar bar bar"}*/httpPost('https://jsonplaceholder.typicode.com/posts',null,//does not send a bodyconsole.log);/*Logs: { "id": 101}*/
Determines if the current runtime environment is a browser so that front-end modules can run on the server (Node) without throwing errors.
Use Array.prototype.includes() on the typeof values of both window and document (globals usually only available in a browser environment unless they were explicitly defined), which will return true if one of them is undefined.
typeof allows globals to be checked for existence without throwing a ReferenceError.
If both of them are not undefined, then the current environment is assumed to be a browser.
Returns the index of the function in an array of functions which executed the fastest.
Use Array.prototype.map() to generate an array where each value is the total time taken to execute the function after iterations times. Use the difference in performance.now() values before and after to get the total time in milliseconds to a high degree of accuracy.
Use Math.min() to find the minimum execution time, and return the index of that shortest time which corresponds to the index of the most performant function.
Omit the second argument, iterations, to use a default of 10,000 iterations. The more iterations, the more reliable the result but the longer it will take.
mostPerformant([()=>{// Loops through the entire array before returning `false`[1,2,3,4,5,6,7,8,9,'10'].every(el=>typeofel==='number');},()=>{// Only needs to reach index `1` before returning false[1,'2',3,4,5,6,7,8,9,10].every(el=>typeofel==='number');}]);// 1
Creates a function that gets the argument at index n. If n is negative, the nth argument from the end is returned.
Use Array.prototype.slice() to get the desired argument at index n.
Parse an HTTP Cookie header string and return an object of all cookie name-value pairs.
Use String.prototype.split(';') to separate key-value pairs from each other.
Use Array.prototype.map() and String.prototype.split('=') to separate keys from values in each pair.
Use Array.prototype.reduce() and decodeURIComponent() to create an object with all key-value pairs.
Converts a number in bytes to a human-readable string.
Use an array dictionary of units to be accessed based on the exponent.
Use Number.toPrecision() to truncate the number to a certain number of digits.
Return the prettified string by building it up, taking into account the supplied options and whether it is negative or not.
Omit the second argument, precision, to use a default precision of 3 digits.
Omit the third argument, addSpace, to add space between the number and unit by default.
Use Math.random to generate a random 24-bit(6x4bits) hexadecimal number. Use bit shifting and then convert it to an hexadecimal String using toString(16).
Converts the values of RGB components to a color code.
Convert given RGB parameters to hexadecimal string using bitwise left-shift operator (<<) and toString(16), then String.padStart(6,'0') to get a 6-digit hexadecimal value.
toCurrency(123456.789,'EUR');// €123,456.79 | currency: Euro | currencyLangFormat: LocaltoCurrency(123456.789,'USD','en-us');// $123,456.79 | currency: US Dollar | currencyLangFormat: English (United States)toCurrency(123456.789,'USD','fa');// ۱۲۳٬۴۵۶٫۷۹ $ | currency: US Dollar | currencyLangFormat: FarsitoCurrency(322342436423.2435,'JPY');// ¥322,342,436,423 | currency: Japanese Yen | currencyLangFormat: LocaltoCurrency(322342436423.2435,'JPY','fi');// 322 342 436 423 ¥ | currency: Japanese Yen | currencyLangFormat: Finnish
Use toLocaleString() to convert a float-point arithmetic to the Decimal mark form. It makes a comma separated string from a number.
Use the modulo operator (%) to find values of single and tens digits.
Find which ordinal pattern digits match.
If digit is found in teens pattern, use teens ordinal.
Returns true if the given value is a number, false otherwise.
Use !isNaN() in combination with parseFloat() to check if the argument is a number.
Use isFinite() to check if the number is finite.
Use Number() to check if the coercion holds.
