Zepto Learning Path--array de-weight and native reduce

Well, start reading the source code of Zepto, the first to deal with the original implementation of trim and reduce, the sense of writing is very compact, which reduce write a little obscure, personal feeling is good. The author of the main zepto is a non-colon party that looks a bit unaccustomed.

　 3 if (String.prototype.trim = = = undefined)//fix for IOS 3.2 4 String.prototype.trim = function () {5 return This.replace (/^\s+|\s+$/g, ")//Trim function similar to PHP 6} 7 8//For IOS 3.x 9//from Https://developer.mozilla.or G/en/javascript/reference/global_objects/array/reduce 10//The function of this method is to be tired like a cumulative processing effect, the previous data processing results used as the next processing 11//For example [ 1,2,3,4,].reduce (function (x, y) {return x+y});     ==> ((1+2) +3) +4, if (Array.prototype.reduce = = = undefined) Array.prototype.reduce = function (fun) {14 if (this = = = void 0 | | this = = NULL) throw new TypeError () var t = Object (this),//t is the copy of the array itself this is Len = T.length >>> 0,//array length k = 0,//array subscript variable accumulator//the variable that holds the result if (typeof fun! = ' function      ') throw new TypeError () if (len = = 0 && arguments.length = 1) throw new TypeError () 21//Take initial value 22 if (arguments.length >= 2) accumulator = arguments[1]//If the parameter length is greater than 2, the second parameter is the initial value of4 if (k in t) {accumulator = t[k++]//Otherwise the first data of the array is used as the initial value of break (++k  >= len) throw new TypeError ()//Under what circumstances will it be executed here???        while (true) 30//iterates over the array, the previous result is passed to the processing function for cumulative processing (K < Len) {32if (k in t) accumulator = fun.call (undefined, accumulator, t[k], K, T)//CORE operation codek++ Accumulator 36}

　　

Zepto Learning Path--array de-weight and native reduce