javascript - Setting Object.prototype.__proto__ instead of just Object.prototype? -

i looking @ article regarding node.js events module:

and in there code:

door.prototype.__proto__ = events.eventemitter.prototype;

which supposedly sets prototype of door object prototype of event.eventemitter.

i believe know difference between prototype , proto code confuses me. questions whether instead of using:

door.prototype.__proto__ = events.eventemitter.prototype;

the author of article did not use line of code:

door.prototype= events.eventemitter.prototype;

this code

door.prototype.__proto__ = events.eventemitter.prototype

makes door.prototype inherit events.eventemitter.prototype.

so prototype chain like

doorinstance -> door.prototype -> events.eventemitter.prototype

this approach similar to

door.prototype = object.create(events.eventemitter.prototype)

the difference modifying [[prototype]] not create new object, has great negative impact on performance.

instead, code

door.prototype = events.eventemitter.prototype

makes door instances inherit directly events.eventemitter.prototype.

that is, won't able add specific methods in door.prototype without polluting events.eventemitter.prototype.

WIKI