Javascript - 初窥

shuaigehua1

于 2010-08-21 21:28:12 发布

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CC 4.0 BY-SA版权

分类专栏： Jscript笔记文章标签： JavaScript prototype Java HTML ViewUI

本文链接：https://blog.youkuaiyun.com/shuaigehua1/article/details/83697696

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本文介绍了使用JavaScript创建自定义对象的方法，并通过实例演示了如何模拟StringBuffer功能以提高字符串拼接效率。

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>chat.html</title>

    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="this is my page">
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">

    <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
   	<script type="text/javascript">
    //定义id抽取函数.....目前只能抽取ID
   	var $=function(id){
   		return document.getElementById(id);
   	};
   	//定义javascript对象:java类
   function FuncObj(name,  job, born){
   		this.name = name;
   		this.job = job;
   		this.born = born;
   		function fn2(){
   			alert(this.new);
   		};
   		new_it:"i am new push by FcunObj fn2";
   };
   //在函数原型操作类:java——对类的操作与方法进行修改
   	FuncObj.prototype.fn=function(){
   		alert("fn");
   	};

   	function showColor() {
 		 alert(this.color);
	};

   	function click_(){
   		showColor();
   		//跟Java也太像了吧~
   		new FuncObj().fn();
   		var obj2 = new FuncObj();
   		alert(obj2.fn2);
   		alert(obj2.new_it);
   	//	obj2.fn2();
   		alert(FuncObj.toString());
   		alert(FuncObj.prototype.fn.toString());
   		alert("enter click");
   		alert($("fst_div"));
   	};


   	</script>

  </head>

  <body>
    <div id="fst_div" ></div>
    <button onclick="click_();">______</button>
    <div></div>
    <div></div>
  </body>
</html>


/**javascript 模拟 StringBuffer();*/

function StringBuffer () {
  this._strings_ = new Array();
}

StringBuffer.prototype.append = function(str) {
  this._strings_.push(str);
};

StringBuffer.prototype.toString = function() {
  return this._strings_.join("");
};
sb.append("123");
sb.append("456");

document.write(sb.toString());

/**测试性能,跟预期结果相反*/
var d1 = new Date();
var str = "";
for (var i=0; i < 10000; i++) {
    str += "text";
}
var d2 = new Date();

document.write("Concatenation with plus: "
 + (d2.getTime() - d1.getTime()) + " milliseconds");

var buffer = new StringBuffer();
d1 = new Date();
for (var i=0; i < 10000; i++) {
    buffer.append("text");
}
var result = buffer.toString();
d2 = new Date();

document.write("<br />Concatenation with StringBuffer: "
 + (d2.getTime() - d1.getTime()) + " milliseconds");