Using the Math Object

The Math object is a built-in JavaScript object that includes math constants and functions. You don’t need to create a Math object; it exists automatically in any JavaScript program. The Math object’s properties represent mathematical constants, and its methods are mathematical functions.

Rounding and Truncating

Three of the most useful methods of the Math object enable you to round decimal values up and down:

• Math.ceil() rounds a number up to the next integer.

• Math.floor() rounds a number down to the next integer.

• Math.round() rounds a number to the nearest integer.

All of these take the number to be rounded as their single parameter. You might notice one thing missing: the capability to round to a decimal place, such as for dollar amounts. Fortunately, you can easily simulate this. Here is a simple function that rounds numbers to two decimal places: