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javascript 的 in 操作符实例详解

作者：xling　来源：蓝色理想　发布时间：2007-10-07 12:00:00　

标签：in,javascript,操作符

以下摘录自 oreilly.JavaScript.The.Definitive.Guide.5th.Edition.Aug.2006

The in Operator

The in operator expects a left-side operand that is or can be converted to a string. It expects a right-side operand that is an object (or array). It evaluates to TRue if the left-side value is the name of a property of the right-side object. For example:

var point = { x:1, y:1 }; // Define an objectvar has_x_coord = "x" in point; // Evaluates to truevar has_y_coord = "y" in point; // Evaluates to truevar has_z_coord = "z" in point; // Evaluates to false; not a 3-D pointvar ts = "toString" in point; // Inherited property; evaluates to true

以下是我的总结，保存自本地运行：

<!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="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head>
<body></body></html><script language="javascript" type="text/javascript">var aa = ["a","b",,"D"];document.write(’var aa = ["a","b",,"D"];’.link("Array")," ");for(var i=-1;i<aa.length + 1;i++){ document.write(i.toString().fontcolor("#cc6600")," in aa : ",(i in aa).toString().italics()," ");}
var bb = {name:"xling",sex:"male"}document.write(’var bb = {name:"xling",sex:"male"}’.link("Object")," ");document.write( "name".fontcolor("#cc6600")," in bb :",("name" in bb).toString().italics()," ", "sex".fontcolor("#cc6600")," in bb :",("sex" in bb).toString().italics()," ", "birthday".fontcolor("#cc6600")," in bb :",("birthday" in bb).toString().italics()," ");
var CC = function(){ this.name = "xling"; this.sex = "male"; this.birthday = "****"; this.getAge = function(){ return "***" } var add = function(){ return ""; }}
var cc = new CC();document.write("var cc = new CC();".link("Instance of CC (Custom Class)")," ");document.write( "name".fontcolor("#cc6600")," in cc :",("name" in cc).toString().italics()," ", "sex".fontcolor("#cc6600")," in cc :",("sex" in cc).toString().italics()," ", "birthday".fontcolor("#cc6600")," in cc :",("birthday" in cc).toString().italics()," ", "getAge()".fontcolor("#cc6600")," in cc :",("getAge" in cc).toString().italics()," ", "add()".fontcolor("#cc6600")," in cc :",("add" in cc).toString().italics()," ");</script>

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javascript 的 in 操作符实例详解

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