Object.create（父级）vs Object.create（父级原型）

Question

My question is about inheritance in javascript. So when you have

child.prototype = Object.create(parent.prototype) 

you are setting the prototype of the child class to a copy of the parent class prototype. If you check in the console the __proto__ property of the child class shows directly __proto__: parent . So far so good. But when you make inheritance like that -

child.prototype = Object.create(parent) 

the __proto__ property of child shows __proto__: function parent() and this function has property prototype which has key-value prototype: parent . The instances of both act the same. Obviously the compiler should take only 1 step more to find the functions in the prototype. There is some kind of difference but is it so significant so Object.create(parent.prototype) is preferred. Can anyone explain this in simple terms?

Answer 1

One of the most confusing pitfalls in javascript is that .prototype and "prototype" are different things. In your example, properties of the first object are resolved via parent.prototype , while the second uses "parent's prototype" aka parent.__proto__ . Consider:

function parent() {};

var a = Object.create(parent.prototype); 
var b = Object.create(parent);

This is the inheritance diagram for this code:

As you can see, prototype chains for a and b are quite different.