YUI原码
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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
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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
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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
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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))
