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Using JavaScript's built-in objects

How to use JavaScript's built-in objects Date, Math, String, Array, and Object

By Gordon Mccomb, JavaWorld.com, 05/01/96

Page 5 of 7

var date_obj = new Date ("January 1 1997 00:00:00")

and

var date_obj = new Date (97, 0, 1, 12, 0, 0)

To use a Date method, append the method to the date object you previously created. For example, to return the current year, use:

var now = new Date();
var yearNow = now.getYear();

For your reference, here are the methods supported by JavaScript's Date object.

Date Methods

Creating arrays and objects

JavaScript supports two (currently) undocumented object constructors: Array and Object. Both do a similar job, but are used in different situations. In JavaScript, an array is really just an object, using numbers or associative names for the array elements. You can create new arrays and objects with either constructor, but for readability, you'll probably want to use the constructor that is most closely associated with your application. Use Array when creating an array; use Object when creating an object.

Let's tackle the Array constructor first.

In JavaScript you can create an array explicitly using your own constructor function. Here is a n example of a basic array constructor.

function makeArray(numElements) {
   this.length = numElements
   for (count = 1; count <= numElements; count++)
      this[count] = 0;
   return (this);
}

To define a new array, you call the makeArray function using the new statement. The following example creates an array with three elements, and fills them with data.

var myArray = new makeArray(3);
myArray[1] = "item 1";
myArray[2] = "item 2";
myArray[3] = "item 3";

Actually, JavaScript doesn't much care how you make your arrays. Though you can define the number of elements in the array, the makeArray function uses this value only to pre-load an initial value in the first three elements. (Element 0 contains the length of the array; element[0] is synonymous with the length property.) You can add additional elements at any time, even after the array has been created.