YUI Array 之 indexOf(索引值|搜索)

YUI原码

YArray.indexOf = Lang._isNative(Native.indexOf) ? function (array, value, from) {
    return Native.indexOf.call(array, value, from);
} : function (array, value, from) {
    // http://es5.github.com/#x15.4.4.14
    var len = array.length;

    from = +from || 0;
    from = (from > 0 || -1) * Math.floor(Math.abs(from));//取整

    if (from < 0) {
        from += len;

        if (from < 0) {
            from = 0;
        }
    }

    for (; from < len; ++from) {
        if (from in array && array[from] === value) {
            return from;
        }
    }

    return -1;
};

 

tangram – indexOf 原码

var T,baidu=T= function(){ 
///import baidu.array;
 
baidu.array.extend({
    indexOf : function (match, fromIndex) {
        baidu.check(".+(,number)?","baidu.array.indexOf");
        var len = this.length;
 
        // 小于 0
        (fromIndex = fromIndex | 0) < 0 && (fromIndex = Math.max(0, len + fromIndex));
 
        for ( ; fromIndex < len; fromIndex++) {
            if(fromIndex in this && this[fromIndex] === match) {
                return fromIndex;
            }
        }
         
        return -1;
    }
});
 return baidu;
}();

underscore原码

_.indexOf = function(array, item, isSorted) {
    if (array == null) return -1;
    var i = 0, l = array.length;
    if (isSorted) {
      if (typeof isSorted == 'number') {
        i = (isSorted < 0 ? Math.max(0, l + isSorted) : isSorted);
      } else {
        i = _.sortedIndex(array, item);
        return array[i] === item ? i : -1;
      }
    }
    if (nativeIndexOf && array.indexOf === nativeIndexOf) return array.indexOf(item, isSorted);
    for (; i < l; i++) if (array[i] === item) return i;
    return -1;
  };

 

qwrap原码

indexOf: function(arr, obj, fromIdx) {
			var len = arr.length;
			fromIdx |= 0; //取整
			if (fromIdx < 0) {
				fromIdx += len;
			}
			if (fromIdx < 0) {
				fromIdx = 0;
			}
			for (; fromIdx < len; fromIdx++) {
				if (fromIdx in arr && arr[fromIdx] === obj) {
					return fromIdx;
				}
			}
			return -1;
		}

 

比较

1.不同在于几个对于起始位置的处理

     a.  YUI的处理看来来复杂，但是它是根据ES5中的标准步骤进行的 

     b.  underscore是唯一一个没用对起始值取整的且不支持负值，但它提供了对大数组提供二进制搜索的功能

     c. underscore针对null做了特殊处理，防止抛出错误，影响后续进行

     d. 比较之下,对于起始位置的处理，倾向于tangram的做法，简洁明了，充分利用了各种运算符的特性

      (fromIndex = fromIndex | 0 ) < 0  &&  (fromIndex = Math.max(0, len + fromIndex))