JavaScript Cheat Sheet

chetsheet.js

==================
//Arrays
==================

//Get Max Value from Array
var arr = [25,1,54,45];
var res = Math.max.apply(Math, arr);


//Random Element from an Array
var arr = ["Apple","Orange","Waterlemon"];
var rand = arr[Math.floor(Math.random()*arr.length)];


//Filter Array from biggest value to lowest
var arr = [1,2,5,7,18];
var res = arr.sort(function(a,b){
	return a < b;
});
	
//Get length of each element in Array
var names = ['HTML', 'CSS', 'JavaScript'];
var nameLengths = names.map(function(name){
	return name.length;
});

//First letter to Uppercase
var names = ["viktor", "andrew", "vlad", "john"];
var toUpper = names.map(function(name) {
	var firstLetter = name[0];
	return firstLetter.toUpperCase() + name.substring(1);
});


/ Shuffles array in place.
 * @param {Array} a items The array containing the items.
 */
function shuffle(a) {
    var j, x, i;
    for (i = a.length; i; i -= 1) {
        j = Math.floor(Math.random() * i);
        x = a[i - 1];
        a[i - 1] = a[j];
        a[j] = x;
    }
}
var myArray = ['1','2','3','4','5','6','7','8','9'];
shuffle(myArray);


//Character remaining in Textarea
var txt = document.getElementById("txtarea");
txt.setAttribute("maxlength", 50);
var maxLength = 50;
var demo = document.getElementById("demo");
var demoTxt = "Character remaining: " + maxLength;
demo.innerHTML = demo.innerHTML + demoTxt;

txt.addEventListener("keyup", function() {
	if(txt.value.length <= maxLength) {
		var result = demo.innerHTML =  " Character remaining: " + (maxLength-txt.value.length); 
	}
});

//If Keyboard key pressed
addEventListener('keypress',function(){
	if(event.which === 13) {}
});


//Removing duplicated item from string
var uniqueList=string.split(',').filter(function(item,i,allItems){
    return i==allItems.indexOf(item);
}).join(',');


========================
String & numbers examples
========================

//reverse numbers with loop
var n = 352, reverse = 0, remainder;
while (n>0) {
	remainder = n%10;
	reverse = reverse * 10 + remainder;
	n = Math.floor(n / 10);
}
console.log(reverse);



==========
//DOM Manipulation
=========

//Extract href from class
var domains = document.querySelectorAll('.a-href');
for(var i = 0; i < domains.length; i++) {
  console.log(domains[i].getAttribute('href'));
}

//Select are to copy
var emailLink = document.querySelector(".js-emaillink");
var btn = document.querySelector(".js-emailcopybtn");
btn.addEventListener("click", function(){
	var range = document.createRange();  
  	range.selectNode(emailLink);  
  	window.getSelection().addRange(range);  
});


//Check if strings contains a keyword from array
ar tp = ['youtube','video'];
var lnk = 'www.youtube.com/video-channel.html';
tp.forEach(function (keyword) {
  if (lnk.indexOf(keyword) > -1) console.log(lnk);
  else console.log("not found in");
});
//Regular expression:
var lnk = 'www.youtube.com/video-channel.html';
var RE = /(youtube|video)/;
if (RE.test(lnk)) console.log('keyword found');
else console.log('keyword not found');

JavaScript Tips

//Reverse String
function reverse(s){
    return s.split("").reverse().join("");
  }