AJAX - The Complete Reference

564 Part IV: Appendixes

You can also use the Array() constructor.

var variable = new Array(element1, element2, ... elementN);

If only one numeric argument is passed it is interpreted as the initial value for the

length property.

There are numerous properties and methods that can be run on arrays.

alert (myArray.length); // 4

myArray = myArray.reverse(); // reverse the array’s items

Beyond the apparent object syntax to manipulate arrays, it is important to note the close

relationship between arrays and objects in JavaScript. Object properties can be accessed not

only as objectName.propertyName but as objectName[‘propertyName’]. However, this does not

mean that array elements can be accessed using an object style; arrayName. 0 would not

access the first element of an array. Arrays are not quite interchangeable with objects in

JavaScript.

JavaScript 1.7, as supported in Firefox 2+, introduces an array-related “destructuring

assignment.” This allows you to access variables in an array outside of the array.

[a, b] = ["val1", "val2"];

alert(a);

alert(b);

// alerts val1 and then val2

One interesting thing we can do with this is a swap assignment without using

temporary variables. Instead of:

var i=1;

var j=2;

var t = i;

i=j;

j=t;

We use:

var i=1;

var j=2;

[i,j] = [j,i];

Another interesting feature is that we can easily return and consume multiple values:

function getBookInformation()

{

var author="Thomas A. Powell";

var subject="Ajax";

return [author, subject];

}

var [bookAuthor, bookSubject] = getBookInformation();

alert(bookAuthor);

alert(bookSubject);