Object.create和继承

Question

What is the difference between the resulting objects in the following examples:

var EventEmitter = require('events').EventEmitter;

var oProto  = Object.create(EventEmitter.prototype);
var oProto2 = Object.create(oProto);

var oConstr  = Object.create(new EventEmitter);
var oConstr2 = Object.create(oConstr);

I suppose oConstr and oConstr2 will have any properties set in the EventEmitter constructor, but is there any other meaningful difference?

Answer 1

Your code is misleading. you use the term oConstr when it's not a constructor function.

oProto -> EventEmitter.prototype -> Object.prototype -> null
oProto2 -> oProto -> EventEmitter.prototype -> Object.prototype -> null

var temp = new EventEmitter;

oConstr -> temp -> EventEmitter.prototype -> Object.prototype -> null
oConstr2 -> oConstr -> etc

The only difference is that temp is not just an object that inherits from EventEmitter it also has own properties augmented from the call to EventEmitter.constructor.call(temp) .

I'd personally recommend you use EventEmitter.prototype and ignore new EventEmitter

Personally I don't ever inherit from EventEmitter , I mix it in