js 字符串扩展

<script type="text/javascript" language="javascript">
　　 String.prototype.trim=function(){
　　    return this.replace(/(^\s*)|(\s*$)/g, "");
　　 }
　　 String.prototype.ltrim=function(){
　　    return this.replace(/(^\s*)/g,"");
　　 }
　　 String.prototype.rtrim=function(){
　　    return this.replace(/(\s*$)/g,"");
　　 }
 
</script>

<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>