对js中startWith和endWith的扩展

http://www.blogjava.net/zhip/archive/2008/07/07/212943.html

<input name="searchContent" id="searchContent" type="text" onclick="test();">
<SCRIPT type="text/javascript" language="JavaScript">
function test(){
var a = "abcdef".startWith("abc");
alert("a : "+a);
var b = "abcdef".endWith("def");
alert("b : "+b);
}
String.prototype.endWith=function(str){
if(str==null||str==""||this.length==0||str.length>this.length)
return false;
if(this.substring(this.length-str.length)==str)
return true;
else
return false;
return true;
}

String.prototype.startWith=function(str){
if(str==null||str==""||this.length==0||str.length>this.length)
return false;
if(this.substr(0,str.length)==str)
return true;
else
return false;
return true;
}

</SCRIPT>