javascript String.indexOf实现

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 < start + length; i++) {
        array.push(this.charAt(i));
    }
    return array.join();
};
String.prototype.indexOf = function(s) {
    for (var i = 0; i < this.length - s.length; i++) {
        if (this.charAt(i) === s.charAt(0) &&
            this.substring(i, s.length) === s) {
            return i;
        }
    }
    return -1;
};

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 < an){
          return -1
        }
        loop:
          for(var i=0;i < n;i++){
          if(this.charAt(i) == a){
            for(var j=1;j < an;j++){
              if(this.charAt(j+i) != sub.charAt(j)){
                continue loop
              }
            }
            return i
          }
        }
        return -1;
      }

       var a = "aabbccb";
      console.log(a.indexOf("bbccb"))//2
      console.log("Blue Whale".indexOf("Blue") )   // returns 0
      console.log("Blue Whale".indexOf("Blute"))   // returns -1

<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> http://proto.layer51.com/d.aspx?f=32 //--------------------------------------------------------------------------- String.prototype.charAt = function(index){ return(substring(this, index+1, 1)); } String.prototype.concat = function(){ var r = this.toString(); for (var i=0; i<arguments.length; ++i){ r += arguments[i]; } return (r); } String.prototype.indexOf = function(sub, i){ if (i == null) i = 0; var size = sub.length; var last = this.length - size + 1; while ((i <= last) && (substring(this, 1+i++, size) != sub)); return (i <= last ? (i-1) : -1); } String.prototype.lastIndexOf = function(sub, i){ size = sub.length; i == null ? i = this.length - size + 1 : ++i; if (sub.length == 0) return i-1; while ((i >= 0) && (substring(this, i--, size) != sub)); return (i == -1 ? -1 : (i)); } String.prototype.slice = function(s, e){ return(substring(this, s+1, e-s)); } String.prototype.split = function(d){ if (d != null){ var r = new Array(); var size = this.length; var c = 0; var n = 0; if (d != ""){ for (var i=0; i<=size; ++i){ if (substring(this, i+1, 1) == d){ r[n] = substring(this, c+1, i-c); c = i+1; ++n; } } if (c != i){ r[n] = substring(this, c+1, i-c); } }else{ for (var i=0; i<s; ++i){ r[i] = substring(this, i+1, 1); } } }else{ r = new Array(this.toString()); } return (r); } String.prototype.substr = function(s, l){ if (l == null){ l = this.length - s; } return(substring(this, s+1, l)); } String.prototype.toUpperCase = function() { var r = this.toString(); out = ""; for (x=0; x<r.length; x++) { upNo = r.charCodeAt(x); if ((upNo>96 && upNo<123) || (upNo>223 && upNo<254)) { out += String.fromCharCode(upNo-32); } else { out += String.fromCharCode(upNo); } } return out; } String.prototype.toLowerCase = function() { var r = this.toString(); out = ""; for (x=0; x<r.length; x++) { upNo = r.charCodeAt(x); if ((upNo>64 && upNo<91) || (upNo>191 && upNo<222)) { out += String.fromCharCode(upNo+32); } else { out += String.fromCharCode(upNo); } } return out; } var s0 = Array(100).join('1'); var s1 = 'abcdefghijklmnopqrstuvwxyz'; s1 = s1.replace(/(?=\w)/g, s0); var s2 = s0 + 'g'; js_abcd(420662993) 18:03:08 在s1中找s2