1. yui-each原码：
遍历YArray.each = YArray.forEach = Lang._isNative(Native.forEach) ? function (array, fn, thisObj) {
Native.forEach.call(array || [], fn, thisObj || Y);
return Y;
} : function (array, fn, thisObj) {
for (var i = 0, len = (array && array.length) || 0; i < len; ++i) {
if (i in array) {
fn.call(thisObj || Y, array[i], i, array);
}
}
return Y; //返回Y,便于链式操作
};
2.tangram-each
tangram遍历var T,baidu=T= function(){
///import baidu;
baidu.each = function( enumerable, iterator, context ) {
var i, n, t, result;
if ( typeof iterator == "function" && enumerable) {
// Array or ArrayLike or NodeList or String or ArrayBuffer
n = typeof enumerable.length == "number" ? enumerable.length : enumerable.byteLength;
if ( typeof n == "number" ) {
// 20121030 function.length
//safari5.1.7 can not use typeof to check nodeList - linlingyu
if (Object.prototype.toString.call(enumerable) === "[object Function]") {
return enumerable;
}
for ( i=0; i<n; i++ ) {
//enumerable[ i ] 有可能会是0
t = enumerable[ i ];
t === undefined && (t = enumerable.charAt && enumerable.charAt( i ));
// 被循环执行的函数，默认会传入三个参数(i, array[i], array)
result = iterator.call( context || t, i, t, enumerable );
// 被循环执行的函数的返回值若为 false 和"break"时可以影响each方法的流程
if ( result === false || result == "break" ) {break;}
}
// enumerable is number
} else if (typeof enumerable == "number") {
for (i=0; i<enumerable; i++) {
result = iterator.call( context || i, i, i, i);
if ( result === false || result == "break" ) { break;}
}
// enumerable is json
} else if (typeof enumerable == "object") {
for (i in enumerable) {
if ( enumerable.hasOwnProperty(i) ) {
result = iterator.call( context || enumerable[ i ], i, enumerable[ i ], enumerable );
if ( result === false || result == "break" ) { break;}
}
}
}
}
return enumerable;
};
return baidu;
}();
3.tangram-array each原码
tangram array遍历var T,baidu=T= function(){
///import baidu.type;
///import baidu.array;
///import baidu.each;
///import baidu.forEach;
baidu.array.extend({
each: function(iterator, context){
return baidu.each(this, iterator, context);
},
forEach: function(iterator, context){
return baidu.forEach(this, iterator, context);
}
});
/// Tangram 1.x Code Start
// TODO: delete in tangram 3.0
baidu.array.each = baidu.array.forEach = function(array, iterator, context) {
var fn = function(index, item, array){
return iterator.call(context || array, item, index, array);
};
return baidu.isEnumerable(array) ? baidu.each(array, typeof iterator == "function" ? fn : "", context) : array;
};
/// Tangram 1.x Code End
return baidu;
}();
4.underscore each 原码：
underscore array遍历var each = _.each = _.forEach = function(obj, iterator, context) {
if (obj == null) return;
if (nativeForEach && obj.forEach === nativeForEach) {
obj.forEach(iterator, context);
} else if (obj.length === +obj.length) {
for (var i = 0, l = obj.length; i < l; i++) {
if (iterator.call(context, obj[i], i, obj) === breaker) return;
}
} else {
for (var key in obj) {
if (_.has(obj, key)) {
if (iterator.call(context, obj[key], key, obj) === breaker) return;
}
}
}
};
5. qwrap – each
qwrap array遍历forEach: function(arr, callback, pThis) {
for (var i = 0, len = arr.length; i < len; i++) {
if (i in arr) {
callback.call(pThis, arr[i], i, arr);
}
}
}
比较
a. YUI会调用原生的forEach，可以用来遍历array,string，不能遍历object,也不会打断遍历
b.tangram最严谨，排除了function具有length属性，但YUI与underscore用了in 这个来排除掉了function,可以返回break 或者false打断遍历，可以用来遍历对象
c. underscore 会调用原生的forEach，可以用来遍历对象，数组，字符串，可以被打断遍历，这个函数在underscore是一个基础的函数，
d. qwrap的最简洁，不会调用原生forEach，也不能打断遍历