Introduction to Javascript

JavaScript, or JS, is most widely used for programming how web pages behave. It also has applications outside of web development, such as it’s use in Node.js and Adobe Acrobat.

What is JavaScript

Characteristics	Styles
Prototype-Based	Object-Oriented
Multi-Paradigm	Imperative
Single-Threaded	Declarative
Dynamic

JavaScript is based on the ECMAScript Language Specification ECMA-424 and the ECMAScript Internationalized API Specification ECMA-402.

NOTE: JavaScript and Java are not the same, and should not be confused.

Using JavaScript

JavaScript can be placed in HTML using the <script></script> element. It can also be called from an external .js file by adding the src="" attribute to the <script> element. Javascript itself has many functions and behaves by rules different from HTML rules.

Variables

Javascript uses variables to store and pass information around. A variable can be declared using var, const, or let. Variable names are unique identifiers which are case sensitive and cannot be the same as existing reserved words (such as keywords for JavaScript).

An example of declaring variables with var would be:

var x = 5
var y = 7
var z = x + y

In this code we declare our x and y variables, and declare a third variable z as the sum of x and y.

Variables can also be strings of text var name = "John" which can be added together using the + operator.