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JavaScript Objects

JavaScript objects are written with curly braces.

Object properties are written as name: value pairs, separated by commas.

Example

var person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"};

The object (person) in the example above has 4 properties: firstName, lastName, age, and eyeColor.

You will learn more about objects later in this tutorial.

JavaScript Arrays

JavaScript arrays are written with square brackets.

Array items are separated by commas.

The following code declares (creates) an array called cars, containing three items (car names):

Example

var cars = ["Saab", "Volvo", "BMW"];

Array indexes are zero-based, which means the first item is [0], second is [1], and so on.

You will learn more about arrays later in this tutorial.

JavaScript Booleans

Booleans can only have two values: true or false.

Example

var x = 5;
var y = 5;
var z = 6;
(x == y)       // Returns true
(x == z)       // Returns false

Booleans are often used in conditional testing.

You will learn more about conditional testing later in this tutorial.


JavaScript Numbers

JavaScript has only one type of numbers.

Numbers can be written with, or without decimals:

Example

var x1 = 34.00;     // Written with decimals
var x2 = 34;        // Written without decimals

Extra large or extra small numbers can be written with scientific (exponential) notation:

Example

var y = 123e5;      // 12300000
var z = 123e-5;     // 0.00123

You will learn more about numbers later in this tutorial.

JavaScript Strings

A string (or a text string) is a series of characters like “John Doe”.

Strings are written with quotes. You can use single or double quotes:

Example

var carName = "Volvo XC60";   // Using double quotes
var carName = 'Volvo XC60';   // Using single quots

You can use quotes inside a string, as long as they don’t match the quotes surrounding the string:

Example

var answer = "It's alright";             // Single quote inside double quotes
var answer = "He is called 'Johnny'";    // Single quotes inside double quotes
var answer = 'He is called "Johnny"';    // Double quotes inside single quotes

You will learn more about strings later in this tutorial.