Working with Arrays

The Array object provides a means of storing and handling a set of other objects. Arrays can store numbers, strings, or other JavaScript objects. There are a couple different ways to create JavaScript arrays. For example, the following statements create three identical versions of the same array:

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var arr = ["one", "two", "three"];
var arr2 = new Array();
arr2[0] = "one";
arr2[1] = "two";
arr3[2] = "three";
var arr3 = new Array();
arr3.push("one");
arr3.push("two");
arr3.push("three");

The first method defines arr and sets the contents in a single statement, using []. The second method creates the arr2 object and then adds items to it, using direct index assignment. The third method creates the arr3 object and then uses the best option for extending arrays: It uses the push() method to push items onto the array.

To determine the number of elements in an array, you can use the length property of the Array object, as in this example:

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var numOfItems = arr.length;

Arrays follow a zero-based index, meaning that the first item is at index 0 and so on. For example, in the following code, the value of variable first will be Monday, and the value of variable last will be Friday:

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var
week = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"];
var first = w [0];
var last = week[week.length-1];

The Array object has several built-in functions that allow you to access and manipulate arrays in various ways. Table 2.7 describes the methods attached to the Array object that allow you to manipulate the array contents.

Table 2.7 Methods to manipulate Array objects

To get you started using the functionality provided in the Array object, the following sections describe some of the common tasks that can be done using Array object methods.