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JavaScript - An Introduction

What is JavaScript?

It's not Java!

JavaScript is an object-oriented computer programming language commonly used to create interactive effects within web browsers.

What is Programming?

Writing instructions for your computer to execute at a later time.

The Modern Web

• The Content Layer (HTML)
• The Design Layer (CSS)
• The Interactive Layer (JavaScript)

What Is JavaScript Used For?

• Adding Fancy Page Interactions - here
• Full Featured Web Apps - here
• Drawing & Animations - here
• Interactive elements - here
• Build a full backend - here
• Go nuts with it - here

Some "Parts" of A Programming Language

• Syntax
• Data Types
• Variables
• Expressions

Syntax

document.getElementById('header');

• document: object
• .: property accessor
• getElementById: property
• (): function call
• 'header': parameter

Data Types

• Number looks like: 1 or 500 or 3.14
• String looks like "Any Message in Quotes"
• Boolean looks like true or false
• Null is an empty value: null
• Undefined is the absence of a value: undefined

Variables

Declare a variable

var firstName;

Assign a value to a variable

firstName = 'Tim';

Shorthand (Declare and assign)

var firstName = 'Tim';

Variables (Rules)

• Begin with letters, $ or _
• Only contain letters, numbers, $ and _
• Case sensitive
• No reserved words - here

Variables (Conventions)

• camelCase vs using _'s
• Choose and stick with a convention

Expressions

Variables can store the result of an expression

var age = 2014 - 1983;
var greeting = "My name is Tim and I am " + age + " years old";
var isOld = age > 100;

Comments

var firstName = "Tim"; // Single Line Comment

/*
  Multi Line
  Comment (Comment Block)
*/
var a = 1;
var b = 2;
var c = 1 + 2;

Arithmetic

var a = 5 + 5; // 10
var b = a * 2; // 20
var c = 25 / 5; // 5
var d = b - c; // 15

Functions

function greet (name) {

  return “Hello, “ + name + “!”;

}

greet(“Tim”); // Hello, Tim!