Web Design in a Nutshell, 3rd Edition

Arrays

Arrays allow you to group multiple values (called members) in a single variable. Standard array values are numerically indexed beginning with 0 and counting upward. They can be declared in a few different ways as well:

    var array_1 = new Array( );  // empty array
    var array_2 = new Array(2); // array with two undefined members
    var array_3 = [];           // shorthand empty array

As with scalars, an array’s values can be set when it is declared:

    var cats  = new Array( 'Sabine', 'Dakota' );
    var names = [ 'Aaron', 'Kelly' ];

or the values can be assigned afterward:

    var cats  = new Array( );
    cats[0]   = 'Sabine';
    cats[1]   = 'Dakota';

An array can contain any sort of data in its members:

    var sabine  = [ 'cat', 'female', 9, true ];
    // Sabine is a 9-year-old female cat that is spayed

even other arrays :

    var cats = new Array( 2 );
    cats[0]  = [ 'Sabine', 'cat', 'female', 9, true ];
    cats[1]  = [ 'Dakota', 'cat', 'male',   8, true ];

An array member can also have its value assigned by a variable:

    var cats   = new Array( 2 );
    var sabine = [ 'cat', 'female', 9, true ];
    var dakota = [ 'cat', 'male',   8, true ];
    cats[0] = sabine;
    cats[1] = dakota;

Associative arrays are a specialized form of array (sometimes referred to as a “hash”) that use keywords as their indexes. The following example uses a few different forms of arrays and scalars:

 var cats = new Array( 2 ); cats['sabine'] = [ 'cat', 'female', 9, true ]; cats['dakota'] = [ 'cat', 'male', 8, true ]; var reps = []; reps['sheldon'] = [ 'tortoise', 'male', 5, false ...