The Ultimate Javascript Cheatsheet

By Gyanendra Kumar Knojiya
Sep 1, 2021 6:30 PM

What is JavaScript?

JavaScript, often abbreviated as JS, is a programming language that conforms to the ECMAScript specification. JavaScript is high-level, often just-in-time compiled, and multi-paradigm. It has curly-bracket syntax, dynamic typing, prototype-based object orientation, and first-class functions.

• First appeared: December 4, 1995; 25 years ago
• Paradigm: event-driven, functional, imperative
• Stable release: ECMAScript 2021 (12th edition) / June 2021; 2 months ago
• Typing discipline: Dynamic, weak, duck
• Designed by: Netscape, Brendan Eich

JavaScript Basics

Set of JavaScript basic syntax to add, execute and write basic programming paradigms in Javascript

On-Page Script

Adding internal JavaScript to HTML

<script type="text/javascript"> //JS code goes here </script>

External JS File

Adding external JavaScript to HTML

<script src="filename.js"></script>

Functions

JavaScript Function syntax

function nameOfFunction () 
{
// function body 
}

DOM Element

Changing content of a DOM Element

document.getElementById("elementID").innerHTML = "Hello World!";

Output

This will print the value of an in JavaScript console

console.log(a);

Conditional Statements

Conditional statements are used to perform operations based on some conditions.

If Statement

The block of code is to be executed, when the condition specified is true.

if (condition) {
// block of code to be executed if the condition is true
}

If-else Statement

If the condition for the if block is false, then the else block will be executed.

if (condition) {
// block of code to be executed if the condition is true
} else {
// block of code to be executed if the condition is false
}

Else-if Statement

A basic if-else ladder

if (condition1) {
// block of code to be executed if condition1 is true
} else if (condition2) {
// block of code to be executed if the condition1 is false and condition2 is true
} else {
// block of code to be executed if the condition1 is false and condition2 is false
}

Switch Statement:

Switch case statement in JavaScript

switch(expression) {
case x:
// code block
break;
case y:
// code block
break;
default:
// code block
}