12 Important JavaScript Functions To Improve Code as a Web Developer on Medium: https://medium.com/@paulknulst

12-important-js-functions-to-improve-code-as-a-web-developer.js

// 1. Valid Json
const isValidJSON = (str) => {
    try {
        JSON.parse(str);
        return true;
    } catch (e) {
        return false;
    }
};

isValidJSON('{"firstname":"Paul","surname":"Knulst"}'); // true
isValidJSON('{"firstname":"Paul",surname:"Knulst"}');   // false
isValidJSON(null); // true


// 2. Days Between Two Dates
const daysBetween = (dateInitial, dateFinal) =>
    (dateFinal - dateInitial) / (1000 * 3600 * 24);

daysBetween(new Date('2022-11-12'), new Date('2023-01-11'));


// 3. Check For Palindrome
const isPalindrome = (str) => str === str.split('').reverse().join('');

isPalindrome('rotator');    // true
isPalindrome('kayak');      // true
isPalindrome('twitter');    // false
isPalindrome('radar');      // true
isPalindrome('challenge');  // false


// 4. Calculate Factorial
const factorial = (number) =>
    number <= 0
        ? (() => {
            throw new TypeError('not possible');
        })()
        : number <= 1
            ? 1
            : number * factorial(number - 1);

factorial(-4);  // Error not possible
factorial(5);   // 120
factorial(9);   // 362880


// 5. Check if number is Power of Two
const isNumberPowerOfTwo = (number) => !!number && (number & (number - 1)) === 0;

isNumberPowerOfTwo(100); // false
isNumberPowerOfTwo(128); // false


// 6. Convert any number to digit
const convertNrToDigitArray = (number) =>
    [...`${number}`].map((el) => parseInt(el));

convertNrToDigitArray(1234);        // [1, 2, 3, 4]
convertNrToDigitArray(23658126);    // [2, 3, 6, 5, 8, 1, 2, 6]


// 7. Calculate Sum of two or more values
const sumOfNumbers = (...arr) => [...arr].reduce((acc, currentValue) => acc + currentValue, 0);

sumOfNumbers(5, 6, 4, 3, 2);            // 20
sumOfNumbers(...[1, 4, 5, 3, 6, 7]);    // 26


// 8. Stringify every object
const stringify = (obj) => {
    for (let [key, value] of Object.entries(obj)) {
        console.log(`${key}: ${value}`);
    }
};

const obj = {
    firstname: 'Paul',
    surname: 'Knulst',
    medium: 'paulknulst',
    homepage: 'https://www.paulsblog.dev',
};

stringify(obj);

// will produce:
// firstname: Paul
// surname: Knulst
// twitter: paulknulst
// homepage: https://www.knulst.dev


// 9. Count elements with reduce function
const names = ['Paul', 'John', 'Paul', 'Steve', 'Harald', 'John', 'Paul'];

const countNames = names.reduce((names, name) => {
    names[name] = (names[name] || 0) + 1;
    return names;
}, {});
console.log(countNames); // {Paul: 3, John: 2, Steve: 1, Harald: 1}


// 10. Measure function time in milliseconds
const startTime = performance.now();
doHeavyFunction();
const endTime = performance.now();
console.log(
    'doHeavyFunction took ' +
    (endTime - startTime) +
    ' milliseconds to execute.'
);

// 11. Cherry-pick keys while using JSON.stringify

const user = {
    id: 1337,
    name: 'Paul Knulst',
    role: 'Senior Engineer',
    company: 'Realcore',
    page: 'https://www.paulsblog.dev',
    github: 'https://www.github.com/paulknulst',
};

JSON.stringify(user, ['name', 'role', 'page']);

// returns
// {
//   "name": "Paul Knulst",
//   "role": "Senior Engineer",
//   "page": "https://www.paulsblog.dev"
// }


// 12. Replacer function to limit output
function replacer(key, value) {
    if (typeof value === 'string' && key !== 'name' && key !== 'page') {
        return undefined;
    }
    return value;
}

const userObject = {
    id: 1337,
    name: 'Paul Knulst',
    role: 'Senior Engineer',
    company: 'Realcore',
    page: 'https://www.paulsblog.dev',
    github: 'https://www.github.com/paulknulst',
};

JSON.stringify(userObject, replacer);

// returns
// {
//   "id": 1337
//   "name": "Paul Knulst",
//   "page": "https://www.paulsblog.dev"
// }


// BONUS: Calculate Execution of any JavaScript function
let count = 0;

console.time('total');
console.time('sub1');
for (let i = 0; i < 10000000; i++) {
    count++;
}
console.timeEnd('sub1');
console.time('sub2');
for (let i = 0; i < 10000000; i++) {
    count++;
}
console.timeEnd('sub2');

console.time('sub3');
for (let i = 0; i < 10000000; i++) {
    count++;
}
console.timeEnd('sub3');
console.timeEnd('total');

// will log:
// sub1: 19.036865234375 ms
// sub2: 19.491943359375 ms
// sub3: 18.36572265625 ms
// total: 57.1337890625 ms