The Book of JavaScript, 2nd Edition

Number

The Number object has some helpful read-only properties.

Properties

MAX_VALUE	FF, IE 4	Read-only: Highest integer possible given the configuration of the browser and the computer it's on
MIN_VALUE	FF, IE 4	Read-only: Lowest integer possible given the configuration of the browser and the computer it's on
NaN	FF, IE 4	Read-only: Not a number, the result if a mathematical operation fails (Math.sqrt(-1), for example); can be tested with the isNaN() function

Example:

if (isNaN(Math.sqrt(-1)))
{
    alert("Get real! You can't take the square root of −1!");
}

NEGATIVE_INFINITY	FF, IE 4	Read-only: Value smaller than Number.MIN_VALUE. You know no number will ever be less than this value.
POSITIVE_INFINITY	FF, IE 4	Read-only: Value bigger than Number.MAX_VALUE. No number ...