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Vanilla JavaScript Quick Reference / Cheatsheet

Vanilla JavaScript Quick Reference / Cheatsheet

Just migrated it from Codepen.io to markdown. Credit goes to David Conner.

Working with DOM Working with JS Working With Functions
Accessing Dom Elements Add/Remove Array Item Add Default Arguments to Function
Grab Children/Parent Node(s) Add/Remove Object Properties Throttle Functions on Resize
Create DOM Elements Conditionals
Add Elements to the DOM Loops
Add/Remove/Toggle/Check Classes Events
Timers
Type Checking

Accessing Dom Elements

// Returns a reference to the element by its ID.
document.getElementById(id);

// Returns an array-like object of all child elements which have all of the given class names.
document.getElementsByClassName(names);

// Returns an HTMLCollection of elements with the given tag name. 
document.getElementsByTagName(name);

// Returns the first element within the document that matches the specified group of selectors.
document.querySelector(selectors);

// Returns a list of the elements within the document (using depth-first pre-order traversal of the document's nodes) 
// that match the specified group of selectors. 
document.querySelectorAll(selectors);

Grab Children/Parent Node(s)

// Get child nodes
var stored = document.getElementById('heading');
var children = stored.childNodes;
console.log(children);

// Get parent node
var parental = children.parentNode;

Create New DOM Elements

// create new elments
var newHeading = document.createElement('h1');
var newParagraph = document.createElement('p');

// create text nodes for new elements
var h1Text= document.createTextNode("This is the fucking header text!");
var paraText= document.createTextNode("This is the fucking Paragraph text!");

// attach new text nodes to new elements
newHeading.appendChild(h1Text);
newParagraph.appendChild(paraText);

// elements are now created and ready to be added to the DOM.

Add Elements to the DOM

// grab element on page you want to add stuff to
var firstHeading = document.getElementById('firstHeading');

// add both new elements to the page as children to the element we stored in firstHeading.
firstHeading.appendChild(newHeading);
firstHeading.appendChild(newParagraph);

// can also insert before like so

// get parent node of firstHeading
var parent = firstHeading.parentNode;

// insert newHeading before FirstHeading
parent.insertBefore(newHeading, firstHeading);

Add Elements to the DOM cont.

Suppose you have the following HTML:

<div id="box1">
  <p>Some example text</p>
</div>
<div id="box2">
  <p>Some example text</p>
</div>
// you can insert another snippet of HTML between #box1 and #box2 
var box2 = document.getElementById("box2");
box2.insertAdjacentHTML('beforebegin', '<div><p>This gets inserted.</p></div>');

// beforebegin - The HTML would be placed immediately before the element, as a sibling.
// afterbegin - The HTML would be placed inside the element, before its first child.
// beforeend - The HTML would be placed inside the element, after its last child.
// afterend - The HTML would be placed immediately after the element, as a sibling.

Add/Remove/Toggle/Check Classes

// grab element on page you want to use
var firstHeading = document.getElementById('firstHeading');

// will remove foo if it is a class of firstHeading
firstHeading.classList.remove("foo");

// will add the class "anotherClass" if one does not already exist
firstHeading.classList.add("anotherclass");

// add or remove multiple classes
firstHeading.classList.add("foo","bar"); 
firstHeading.classList.remove("foo","bar");

// if visible class is set remove it, otherwise add it
firstHeading.classList.toggle("visible");

// will return true if it has class of "foo" or false if it does not
firstHeading.classList.contains("foo");

Add/Remove Array Item

// create an empty array
var myArray = [];

// create array with items. Can store any type
var myOtherArray = [myArray, true, "A random string"];

// call specific value in an array
myOtherArray[0];
// will return myArray

// change value for this item
myOtherArray[0] = false;
// will now return false


// add to end of array
myOtherArray[myOtherArray.length] = "new stuff";
// will return the new item "new stuff"

// or you can use push()
myOtherArray.push("new stuff");
// will return new length of array


// you can remove this last item by using pop()
myOtherArray.pop();
// will return the last item of the array and will have removed it from myOtherArray


// shift and unshift will do the same for the begging of the Array
myOtherArray.shift();
// will remove and return first item of array

myOtherArray.unshift(1,2);
// this will add 1 and 2 to beginning of array and return new length

// you can use delete keyword but turn value to undefine and not shorten length. so we use splice()
myOtherArray.splice(2, 1);
// this will remove and return  the third item only. 
// first arg is where to start and second is how many things to splice. this example is 1.

Add/Remove Object Properties

// create an object
var newObject = {};

// add a property to object
newObject.newPropName = "super fly";

// or other syntax
newObject['other new prop name'] = "mildly fly";

// Now newObject.newPropName will return super fly
newObject.newPropName;

// now to delete
delete newObject.newPropName;

Conditionals

// If Else statements
var a = 1;
var b = 2;

if( a < b ) {
  console.log('the if is true!');
} else {
  console.log('the if is false!');
}


// Multi If Else statements
var a = 1;
var b = 2;
var c = 3;

if( a > b ) {
  console.log('the if is true!');
} else if(a > c) {
  console.log('OK, THIS if is Ture!');
} else {
  console.log('None of these were true');
}


// Ternary operators. same as if else
var a = 1;
var b = 2;

a === b ? console.log('The statement is true') : console.log('The statement is false');

// switch statements
var a = 4;
switch (a) {
  case "Oranges":
    console.log("Orange? really?");
    break;
  case 1:
    console.log("a is equal to 1.");
    break;
  case 2:
    console.log("a is equal to 2.");
    break;
  case 3:
    console.log("a is equal to 3.");
    break;
  case 4:
    console.log("a is equal to 4.");
    break;
  default:
    console.log("I run if no one else is true.");
}

Loops

// while loop
var i = 0;
while( i < 10 ) {
  console.log(i);
  i += 1
}


// do while loop
var i = 0;
do {
  console.log(i);
  i += 1
} while( i < 10 )


// for loop
for ( var i = 0; i < 10; i++ ) {
   console.log(i);
}

// for in statments
var obj = {a:1, b:2, c:3};
    
for ( var prop in obj ) {
  // check if property is inherited or not
  if(obj.hasOwnProperty(prop)) {
    console.log("obj." + prop + " = " + obj[prop]);
  }
}

Events

var newElement = document.getElementsByTagName('h1');

newElement.onclick = function() {
  console.log('clicked');
};

newElement.addEventListener("focus", function(event) {
    console.log('focused');
}, false);

newElement.removeEventListener("focus", function(event) {
    console.log('focused');
}, false);


window.onload = function() {
  console.log("Im loaded");
};

Timers

function simpleMessage() {
  alert("This is just a simple alert");
}

// set time out
window.setTimeout(simpleMessage, 5000);

// if you wanted to clear the timer.
var timer = window.setTimeout(simpleMessage, 5000);
window.clearTimeout(timer);

// set interval. will repeat every  5000ms
window.setInterval(simpleMessage, 5000);

// if you wanted to clear the intervals.

var intervalHandler = window.setInterval(simpleMessage, 5000);
window.clearInterval(intervalHandle);

Type Checking

var myNumber = 1;
var myString = "some Text";
var bools = true;
var myArray = [];
var myObj = {};
var notNumber = NaN;
var nullified = null;

typeof myNumber;
// returns "number"

typeof myString;
// returns "string"

typeof bools;
// returns "boolean"

typeof myArray;
// returns "object". 

// Not super helpful so must check if it has length property to see if it is an array.
typeof myArray === 'object' && myArray.hasOwnProperty('length');
// returns true

typeof myObj;
// returns "object". Must do the same test as above but expect false back from check.

typeof notNumber;
// returns "number". this is confusing but returns this as NaN is part of the global Number object.

// must check if isNaN()
typeof notNumber === 'number' && isNaN(notNumber);
// returns true if type of is "number" and is still NaN

Add Default Arguments to Function

// you provide defaults inside your function

var myFunction = function myFunction(arg1, arg2) {
  var arg1 = (typeof arg1 !== 'undefined') ? arg1 : "default argument one";
  var arg2 = (typeof arg2 !== 'undefined') ? arg2 : "default argument two";
  console.log(arg1 + " & " + arg2);
};

Throttle Functions on Resize

var optimizedResize = (function() {

  var callbacks = [];
  var running = false;

  // fired on resize event
  function resize() {

    if (!running) {
      running = true;

      if (window.requestAnimationFrame) {
        window.requestAnimationFrame(runCallbacks);
      } else {
          setTimeout(runCallbacks, 66);
      }
    }

  }

  // run the actual callbacks
  function runCallbacks() {
    callbacks.forEach(function(callback) {
      callback();
    });
    running = false;
  }

  // adds callback to loop
  function addCallback(callback) {
    if (callback) {
      callbacks.push(callback);
    }
  }
  
  return {
    // initalize resize event listener
    init: function(callback) {
      window.addEventListener('resize', resize);
      addCallback(callback);
    },
    // public method to add additional callback
    add: function(callback) {
      addCallback(callback);
    }
  }
  
}());

// start process
optimizedResize.init(function() {
    console.log('Resource conscious resize callback!')
});
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