JavaScript & DHTML Cookbook

Chapter 2. Numbers and Dates

Introduction

Designers of friendly scripting languages might have nonprogrammers in mind when they first define the scope of their languages, but it’s difficult for any such language to be taken seriously by professional programmers unless some of the nerdy basics are there. Math may be anathema to scripters not schooled in computer science, but even an accessible language such as JavaScript has a solid complement of features to accommodate the kinds of arithmetic, trigonometric, and other operations typically supported by a programming language. Date manipulation—also numerically intensive, as it turns out—is well supported in JavaScript as well. This chapter includes recipes for both of these areas.

JavaScript Numbers

For most scripters, the interior details about how JavaScript treats numbers is of little importance. In fact, the more you know about programming languages and different types of numbers, the more you need to forget in order to use JavaScript numbers. Unlike other languages, JavaScript has only one kind of number data type. All integers and floating-point values are represented by the same data type in JavaScript: number .

Internally, a JavaScript number is an IEEE double-precision 64-bit value. JavaScript provides a usable range of number values from 2.2E-208 to 1.79E+308 (boundary values obtainable by the static Number object properties Number.MIN_VALUE and Number.MAX_VALUE, respectively). JavaScript treats numbers beyond these limits ...