javascript - Why use Object.create inside this reduce callback? -

so while working on #19 of fine tutorial - http://jhusain.github.io/learnrx/, find exercise works without using object.create. (see commented-out lines)

1. point of creating copy of accumulatedmap? other showing possible...

function() {     var videos = [         {             "id": 65432445,             "title": "the chamber"         },         {             "id": 675465,             "title": "fracture"         },         {             "id": 70111470,             "title": "die hard"         },         {             "id": 654356453,             "title": "bad boys"         }     ];      // expecting output...     // [     //     {     //         "65432445": "the chamber",     //         "675465": "fracture",     //         "70111470": "die hard",     //         "654356453": "bad boys"     //     }     // ]     return videos.         reduce(function(accumulatedmap, video) {              // object.create() makes fast copy of accumulatedmap             // creating new object , setting accumulatedmap             // new object's prototype.             // new object empty , has no members of own,             // except pointer object on based. if             // attempt find member on new object fails, new object             // silently attempts find member on prototype.             // process continues recursively, each object checking             // prototype until member found or reach first object             // created.             // if set member value on new object, stored             // directly on object, leaving prototype unchanged.             // object.create() perfect functional programming because             // makes creating new object different member value             // cheap changing member on original object!              //var copyofaccumulatedmap = object.create(accumulatedmap);              //copyofaccumulatedmap[video.id] = video.title;             accumulatedmap[video.id] = video.title;            //return copyofaccumulatedmap;             return accumulatedmap;         },         // use empty map initial value instead of first item in         // list.         {}); } 

2 , if do using copyofaccumulatedmap, end object this

which looks intriguing, puzzling because cannot same thing code here

var fruit = { 'taste' : 3 };  var apple = object.create(fruit);     apple['size'] = 7;  var apple = object.create(fruit);     apple['hardness'] = 6;  var apple = object.create(fruit);     apple['weight'] = 10;  console.log(apple.taste); console.log(apple.size);     // undefined expect console.log(apple.hardness); // undefined expect console.log(apple.weight); 

so allows object in exercise have chained prototypes doesn't allow apple same?

you kind of answered own question: object.create makes prototype chain. object.create takes parameter prototype object object being created.

var copyofaccumulatedmap = object.create(accumulatedmap); 

the old accumulatedmap being used prototype copyofaccumulatedmap. copy returned, accumulatedmap next time through.