Book Image

Object-Oriented JavaScript - Second Edition

Book Image

Object-Oriented JavaScript - Second Edition

Overview of this book

JavaScript is the behavior, the third pillar in today's paradigm that looks at web pages as something that consists of clearly distinguishable parts: content (HTML), presentation (CSS) and behavior (JavaScript). Using JavaScript, you can create not only web pages but also desktop widgets, browser and application extensions, and other pieces of software. It's a pretty good deal: you learn one language and then code all kinds of different applications. While there's one chapter specifically dedicated to the web browser environment including DOM, Events and AJAX tutorials, the rest is applicable to the other environments Many web developers have tried coding or adopting some bits of JavaScript, but it is time to "man up" and learn the language properly because it is the language of the browser and is, virtually, everywhere. This book starts from zero, not assuming any prior JavaScript programming knowledge and takes you through all the in-depth and exciting futures hidden behind the facade. Once listed in the "nice to have" sections of job postings, these days the knowledge of JavaScript is a deciding factor when it comes to hiring web developers. After reading this book you'll be prepared to ace your JavaScript job interview and even impress with some bits that the interviewer maybe didn't know. You should read this book if you want to be able to take your JavaScript skills to a new level of sophistication.
Table of Contents (19 chapters)
Object-Oriented JavaScript Second Edition
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Built-in Functions
Regular Expressions
Index

Number


This creates number objects:

> var n = new Number(101);
> typeof n;
"object"
> n.valueOf();
101

The Number objects are not primitive objects, but if you use any Number.prototype method on a primitive number, the primitive will be converted to a Number object behind the scenes and the code will work.

> var n = 123;
> typeof n;
"number"
> n.toString();
"123"

Used without new, the Number constructor returns a primitive number.

> Number("101");
101
> typeof Number("101");
"number"
> typeof new Number("101");
"object"

Members of the Number constructor

Property/method

Description

Number.MAX_VALUE

A constant property (cannot be changed) that contains the maximum allowed number.

> Number.MAX_VALUE;
1.7976931348623157e+308

Number.MIN_VALUE

The smallest number you can work with in JavaScript.

> Number.MIN_VALUE;
5e-324

Number.NaN

Contains the Not A Number number. The same as the global NaN.

> Number.NaN; 
NaN

NaN is not equal to anything including itself.

> Number.NaN === Number.NaN;
false

Number.POSITIVE_INFINITY

The same as the global Infinity number.

Number.NEGATIVE_INFINITY

The same as -Infinity.

The Number.prototype members

Property/method

Description

toFixed(fractionDigits)

Returns a string with the fixed-point representation of the number. Rounds the returned value.

> var n = new Number(Math.PI);
> n.valueOf();
3.141592653589793
> n.toFixed(3);
"3.142"

toExponential(fractionDigits)

Returns a string with exponential notation representation of the number object. Rounds the returned value.

> var n = new Number(56789);
> n.toExponential(2);
"5.68e+4"

toPrecision(precision)

String representation of a number object, either exponential or fixed-point, depending on the number object.

> var n = new Number(56789);
> n.toPrecision(2);
"5.7e+4"
> n.toPrecision(5);
"56789"
> n.toPrecision(4);
"5.679e+4"
> var n = new Number(Math.PI);
> n.toPrecision(4);
"3.142"