Why Array cannot add prototype with literals?

Question

var a=[1,2,3,4]

function Demo(){}

Array.prototype={
  foo:function(){
    alert(1)
  }
}//a.foo is not a function

Array.prototype.foo=function(){
  alert(1)
}//alert(1)

a.foo()

Demo.prototype={
  foo:function(){
    alert(1)
  }
}

var b=new Demo()
b.foo()//alert(1)

Why can't Array add prototype with literals? Also, why does it work when I use a constructor?

Here is an example: https://jsbin.com/zowalu/edit?js,console

Matt Way · Accepted Answer · 2015-07-28 02:23:25Z

2

You cannot replace the Array.prototype object (which is what you are trying to do in the first example), as Array.prototype is read-only.

Your second example works because you are simply adding a key to the prototype, not replacing it.

The third example works, because Demo is an object of your design, whereby the prototype is not read-only.

answered Jul 28, 2015 at 2:23

Matt Way

33.3k10 gold badges85 silver badges86 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Dd Xia Over a year ago

Thanks,i know,you mean i try to replace all in first example

RobG Over a year ago

Even if the first case worked, a is constructed before the replacement of Array.prototype so would still reference the original prototype anyway.

Collectives™ on Stack Overflow

Why Array cannot add prototype with literals?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related