JavaScript Cookbook

Chapter 4. Working with Numbers and Math

4.0. Introduction

Numbers and numeric operations in JavaScript are managed by two different JavaScript objects: Number and Math.

Like the String and RegExp objects discussed in earlier chapters, numbers can be both a literal value and an object. No surprises there, but the Math object is different: it has no constructor, and all properties and methods are accessed directly from the object.

The Number Object and Number Literal

Numbers in JavaScript are floating point, though there may not be a decimal component present. If no decimal is present, they act as if they’re integers:

var someValue = 10; // treated as integer 10, in base 10

Numbers can be defined in the range of –2⁵³ to 2⁵³. Most numbers in JavaScript are literal values, assigned as values to variables, and used in various computations:

var myNum = 3.18;
var newNum = myNum * someValue;

You can also construct a Number using a constructor method:

var newNum = new Number(23);

You can assign a literal number to a variable, but when you access a Number method on the variable, a Number object is created to wrap the literal value, which is discarded when the method is finished.

The Number object’s methods provide various display operations, such as providing an exponential notation:

var tst = .0004532;
alert(tst.toExponential()); // outputs 4.532e-4

In addition, there are several static Number properties, which can only be accessed via the Number object directly:

alert(Number.MAX_VALUE); // outputs 1.7976931348623157e+308 ...