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<html><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Keywords" name="Keywords"content="JavaScript, examples, JavaScript: The Definitive Guide"><title>Example 9-2 from JavaScript: The Definitive Guide, Fifth Edition</title><style>body { font-family: arial, sans-serif}.lefttitle { font: bold x-small arial, sans-serif; margin: 5px; letter-spacing: .15em; text-transform:uppercase;}.leftcaption { font: italic x-small sans-serif; margin-bottom: 20px;}#banner { font-family:sans-serif; color:#333; font-size:x-large; font-weight:normal; padding:15px; padding-top: 3px; border-bottom:4px double #666;}#banner h1 { font-size: x-large; margin: 0px; padding: 0px;}#banner .description { font-size:large; margin-left: 2px;}pre { border: solid black 1px; background-color: #ddd; padding: 10px; margin: 0px;} </style></script></head><body><div id="banner"><h1>davidflanagan.com/javascript5</h1><span class="description">Example 9-2 from<i>JavaScript: The Definitive Guide, Fifth Edition</i></span></div><div style="float: left; 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text-align: right"><a href="index.html" tppabs="http://www.davidflanagan.com/javascript5/index.html">Table of Examples</a></div><pre>/* * Complex.js: * This file defines a Complex class to represent complex numbers. * Recall that a complex number is the sum of a real number and an * imaginary number and that the imaginary number i is the * square root of -1. *//* * The first step in defining a class is defining the constructor * function of the class. This constructor should initialize any * instance properties of the object. These are the essential * "state variables" that make each instance of the class different. */function Complex(real, imaginary) { this.x = real; // The real part of the number this.y = imaginary; // The imaginary part of the number}/* * The second step in defining a class is defining its instance * methods (and possibly other properties) in the prototype object * of the constructor. Any properties defined in this object will * be inherited by all instances of the class. Note that instance * methods operate implicitly on the this keyword. For many methods, * no other arguments are needed. */// Return the magnitude of a complex number. This is defined// as its distance from the origin (0,0) of the complex plane.Complex.prototype.magnitude = function() { return Math.sqrt(this.x*this.x + this.y*this.y);};// Return a complex number that is the negative of this one.Complex.prototype.negative = function() { return new Complex(-this.x, -this.y);};// Add a complex number to this one and return the sum in a new object.Complex.prototype.add = function(that) { return new Complex(this.x + that.x, this.y + that.y);}// Multiply this complex number by another and return the product as a// new Complex object.Complex.prototype.multiply = function(that) { return new Complex(this.x * that.x - this.y * that.y, this.x * that.y + this.y * that.x);}// Convert a Complex object to a string in a useful way.// This is invoked when a Complex object is used as a string.Complex.prototype.toString = function() { return "{" + this.x + "," + this.y + "}";};// Test whether this Complex object has the same value as another.Complex.prototype.equals = function(that) { return this.x == that.x && this.y == that.y;}// Return the real portion of a complex number. This function// is invoked when a Complex object is treated as a primitive value.Complex.prototype.valueOf = function() { return this.x; }/* * The third step in defining a class is to define class methods, * constants, and any needed class properties as properties of the * constructor function itself (instead of as properties of the * prototype object of the constructor). Note that class methods * do not use the this keyword: they operate only on their arguments. */// Add two complex numbers and return the result.// Contrast this with the instance method add()Complex.sum = function (a, b) { return new Complex(a.x + b.x, a.y + b.y);};// Multiply two complex numbers and return the product.// Contrast with the instance method multiply()Complex.product = function(a, b) { return new Complex(a.x * b.x - a.y * b.y, a.x * b.y + a.y * b.x);};// Here are some useful predefined complex numbers.// They are defined as class properties, and their names are in uppercase// to indicate that they are intended to be constants (although it is not// possible to make JavaScript properties read-only).Complex.ZERO = new Complex(0,0);Complex.ONE = new Complex(1,0);Complex.I = new Complex(0,1);</pre><div class="lefttitle" style="padding:0px; text-align: right"><a href="index.html" tppabs="http://www.davidflanagan.com/javascript5/index.html">Table of Examples</a></div><p><script type="text/javascript">amazon_ad_tag="davidflanagancom"; amazon_ad_width="300"; amazon_ad_height="250"; amazon_ad_logo="hide";</script><script type="text/javascript" src="../../www.assoc-amazon.com/s/ads.js" tppabs="http://www.assoc-amazon.com/s/ads.js"></script></div></body></html>?? 快捷鍵說明
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