学步园

群里abcd提出问题,现在有以下三个实现，欢迎大家参与(注意，为了兼容IE6，不能使用str[i]，要用str.charAt(i);不能使用slice，replace等原生函数)：

GrayZhang的实现

String.prototype.substring = function(start, length) {
    var array = [];
    for (var i = start; i 

我的实现：
//by 司徒正美 2011.8.18
String.prototype.indexOf = function(sub){
        var a = sub.charAt(0),an = sub.length,n = this.length;
        if(n == an){
          return this == sub ? 0 : -1
        }
        if(n 




<p>abcd的实现：</p>
<pre class="brush:js;gutter:false;toolbar:false;">

function indexOf(s, t) {
	if (s.length) {
		var back = false;
		var i = 0;

		for (var j = 0; j < t.length; ++j) {
			if (s.charAt(i) != t.charAt(j)) {
				do {
					if (++i >= s.length) return -1;
					if (s.charAt(i) == t.charAt(j)) {
						if (j) back = true;
						break;
					}
				}
				while (true);
			}
			if (back) {
				for (var k = 1; k <= j; k++)
					if (s.charAt(i - k) != t.charAt(j - k))
						continue;
				back = false;
			}
		}
		return i - j + 1;
	}
	return t.length && -1;
} 
</pre>
<p>http://proto.layer51.com/d.aspx?f=32</p>
<p>//---------------------------------------------------------------------------<br />
String.prototype.charAt = function(index){<br />
    return(substring(this, index+1, 1));<br />
}  </p>
<p>String.prototype.concat = function(){<br />
    var r = this.toString();<br />
    for (var i=0; i<arguments.length r arguments return string.prototype.indexof="function(sub," i if null var size="sub.length;" last="this.length" while sub : string.prototype.lastindexof="function(sub," i-1>= 0) && (substring(this, i--, size) != sub));<br />
    return (i == -1 ? -1 : (i));<br />
}  </p>
<p>String.prototype.slice = function(s, e){<br />
    return(substring(this, s+1, e-s));<br />
}  </p>
<p>String.prototype.split = function(d){<br />
    if (d != null){<br />
        var r = new Array();<br />
        var size = this.length;<br />
        var c = 0;<br />
        var n = 0;<br />
        if (d != ""){<br />
            for (var i=0; i96 && upNo223 && upNo64 && upNo191 && upNo</p>
<p></arguments.length>