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Re: Does copying the prototype reference from another constructor function maintain the prototype chain?

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GGolf <invalid@invalid.com> wrote:
> I've been a Javascript dabbler for a few years, and have just embarked 
> on learning more advanced stuff.
> 
> I have the following question in a tutorial by John Resig:
> 
> At http://ejohn.org/apps/learn/#76, Resig mentions that only the 
> following maintains the prototype chain:
> 
> Ninja.prototype = new Person();
> 
> However, I notice that even the following statement makes all the test 
> statements pass:
> 
> Ninja.prototype = Person.prototype;
> 
> Does it mean that using "Person.prototype" can actually be used instead 
> of "new Person()"?

Yes.

"Ninja.prototype = Person.prototype;" does create prototype inheritance, 
but with only 2 levels: Person and Object. The inheritance from Ninja and 
Person is the exact same.

function Person(){}

function Ninja(){}
Ninja.prototype=new Person();

var ninjaNew=new Ninja();
console.log('ninjaNew');
console.log(
  ninjaNew.__proto__===Ninja.prototype
); //true
console.log(
  ninjaNew.__proto__.__proto__===Person.prototype
); //true
console.log(
  ninjaNew.__proto__.__proto__.__proto__===Object.prototype
); //true

Ninja.prototype=Person.prototype;
var ninjaProto=new Ninja();
console.log('ninjaProto');
console.log(
  ninjaProto.__proto__===Ninja.prototype
); //true
console.log(
  ninjaProto.__proto__===Person.prototype
); //true
console.log(
  ninjaProto.__proto__.__proto__===Person.prototype
); //false
console.log(
  ninjaProto.__proto__.__proto__===Object.prototype
); //true

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Thread

Does copying the prototype reference from another constructor function maintain the prototype chain? GGolf <invalid@invalid.com> - 2013-01-05 12:39 +0530
  Re: Does copying the prototype reference from another constructor function maintain the prototype chain? JJ <jaejunks@nah.meh> - 2013-01-05 10:57 +0000
    Re: Does copying the prototype reference from another constructor function maintain the prototype chain? David Mark <dmark.cinsoft@gmail.com> - 2013-01-05 06:44 -0800
  Re: Does copying the prototype reference from another constructor function maintain the prototype chain? David Mark <dmark.cinsoft@gmail.com> - 2013-01-05 06:43 -0800
  Re: Does copying the prototype reference from another constructor function maintain the prototype chain? John G Harris <john@nospam.demon.co.uk> - 2013-01-05 15:53 +0000
    Re: Does copying the prototype reference from another constructor function maintain the prototype chain? David Mark <dmark.cinsoft@gmail.com> - 2013-01-05 08:51 -0800
  Re: Does copying the prototype reference from another constructor function maintain the prototype chain? Scott Sauyet <scott.sauyet@gmail.com> - 2013-01-05 12:25 -0800
  Re: Does copying the prototype reference from another constructor function maintain the prototype chain? Luc Yen <luc@goal.tw> - 2013-01-05 13:23 -0800

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