--- /dev/null
+var aFunction = require('./_a-function')
+ , toObject = require('./_to-object')
+ , IObject = require('./_iobject')
+ , toLength = require('./_to-length');
+
+module.exports = function(that, callbackfn, aLen, memo, isRight){
+ aFunction(callbackfn);
+ var O = toObject(that)
+ , self = IObject(O)
+ , length = toLength(O.length)
+ , index = isRight ? length - 1 : 0
+ , i = isRight ? -1 : 1;
+ if(aLen < 2)for(;;){
+ if(index in self){
+ memo = self[index];
+ index += i;
+ break;
+ }
+ index += i;
+ if(isRight ? index < 0 : length <= index){
+ throw TypeError('Reduce of empty array with no initial value');
+ }
+ }
+ for(;isRight ? index >= 0 : length > index; index += i)if(index in self){
+ memo = callbackfn(memo, self[index], index, O);
+ }
+ return memo;
+};
\ No newline at end of file