javascript 的 in 操作符实例详解
作者：xling 来源：蓝色理想 时间：2007-10-07 12:00:00
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"),"<br />");for(var i=-1;i<aa.length + 1;i++){ document.write(i.toString().fontcolor("#cc6600")," in aa : ",(i in aa).toString().italics(),"<br />");}
var bb = {name:"xling",sex:"male"}document.write(’var bb = {name:"xling",sex:"male"}’.link("Object"),"<br />");document.write( "name".fontcolor("#cc6600")," in bb :",("name" in bb).toString().italics(),"<br />", "sex".fontcolor("#cc6600")," in bb :",("sex" in bb).toString().italics(),"<br />", "birthday".fontcolor("#cc6600")," in bb :",("birthday" in bb).toString().italics(),"<br />");
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)"),"<br />");document.write( "name".fontcolor("#cc6600")," in cc :",("name" in cc).toString().italics(),"<br />", "sex".fontcolor("#cc6600")," in cc :",("sex" in cc).toString().italics(),"<br />", "birthday".fontcolor("#cc6600")," in cc :",("birthday" in cc).toString().italics(),"<br />", "getAge()".fontcolor("#cc6600")," in cc :",("getAge" in cc).toString().italics(),"<br />", "add()".fontcolor("#cc6600")," in cc :",("add" in cc).toString().italics(),"<br />");</script>
标签：in,javascript,操作符
0
投稿猜你喜欢
Oracle 安装和卸载问题收集（集合篇）第1/6页
2009-07-02 12:20:00
Asp WinHttp.WinHttpRequest.5.1 对象使用详解
2012-05-02 10:15:27
asp 实现当有新信息时播放语音提示的效果
2011-03-31 11:00:00
商业价值与用户价值的平衡
2008-12-10 18:42:00
有关asp的系统变量ServerVariables (“HTTP_USER_AGENT“)？
2009-10-29 12:12:00
浏览器中的内存泄露（续）解决方案
2008-05-03 17:14:00
栅格:一以贯之
2008-07-22 12:19:00
PHP桥接模式Bridge Pattern的优点与实现过程
2023-05-25 06:53:44
屏幕分辨率和布局简述
2009-04-20 20:27:00
语义化提高页面质量
2007-10-07 11:56:00
SQL查询重复记录
2011-03-27 09:06:00
Dreamweaver实现flash透明背景
2008-05-04 09:35:00
解析xml字符串的函数
2008-06-10 12:37:00
asp随机获取access数据库中的一条记录
2007-08-15 13:11:00
ASP万用分页程序
2007-09-21 12:45:00
什么是UE，UED？
2008-07-24 13:26:00
在ASP应用程序中加入智能搜索
2007-09-18 13:15:00
如何提升JavaScript的运行速度（递归篇）
2010-05-17 13:30:00
FrontPage XP设计教程4——Css样式表的应用
2008-10-11 12:25:00
用户不需要信息快餐
2009-02-25 12:34:00