Using JavaScript's Built-in Objects

In this column, we'll tell you what <br>they are and how to use them

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

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The Math object is static, so you don't need to create a new Math object in order to use it. To access the properties and method of the Math object, you merely specify the Math object, along with the method or property you wish. For example, to return the value of pi, you use:

var pi = Math.PI;

Similarly, to use a math method you provide the name of the method, along with the parameters you wish to use. For example, to round the value of pi, you'd use:

var pi = Math.PI;
var pieAreRound = Math.round(pi);       // displays 3

Note that you must specify the Math object by name for each Math method/property you wish to use. JavaScript does not recognize the keywords PI and round all by themselves. Exception: you may use the with statement to associate the names of methods and properties with the Math object. This technique is a handy space-saver when you must use several Math properties and methods. The previous example can be written as

with (Math) {
        var pi = PI;
        var pieAreRound = round(pi);
        alert (pieAreRound)
}

For your reference, here are the properties and methods supported by JavaScript's Math object.

Asking JavaScript for a date

JavaScript treats the Date object like a constructor class. To use Date you must create a new Date object; you can then apply the various Date methods to get and set dates. (The Date object has no properties.) If you're familiar with the Date class in Java, you'll find the properties of the JavaScript Date object largely the same. The most commonly used methods are the get methods, which obtain the time and date of the value in the Date object. These methods are: