How can I stop pass by reference an object stored in prototype?

Question

Can I define an object as a prototype member? If yes then how can I stop the call by reference of an instantiated object?

function MediaUser (){
}

MediaUser.prototype.oThumb = {sUrl: 'noImage.png'};

var oMediaUser = new MediaUser();
var oMediaUser2 = new MediaUser();

oMediaUser.oThumb.sUrl = "a.png";

console.log(oMediaUser2.oThumb.sUrl); // prints a.png

Michał Perłakowski · Accepted Answer · 2016-05-23T18:36:51.553

2

Everything you define in prototype is shared by all objects. You have to put that inside the constructor if you want it to be different for all instances:

function MediaUser (){
  this.oThumb = {sUrl: 'noImage.png'}
}

var oMediaUser = new MediaUser();
var oMediaUser2 = new MediaUser();

oMediaUser.oThumb.sUrl = "a.png";

console.log(oMediaUser2.oThumb.sUrl); // prints noImage.png

edited May 23 '16 at 18:36

answered May 23 '16 at 18:36

Michał Perłakowski

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so @Gothdo, anytime if I want to add an object inside another object, I always have to put it as an instance member rather than prototype member ? – Gan May 23 '16 at 18:41

score 0 · Answer 2 · answered May 23 '16 at 18:45

0

In fact when you are looking for separate value for each object , get rid of thet prototype property altogether

function MediaUser (url){
 this.sUrl = url || 'noImage.png';
}


var oMediaUser = new MediaUser("a.png");
var oMediaUser2 = new MediaUser();

console.log(oMediaUser.sUrl); // prints a.png

console.log(oMediaUser2.sUrl); // prints noImage.png

answered May 23 '16 at 18:45

sapy

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Don't use the `a = a || b` construct, see http://stackoverflow.com/questions/2802055/what-does-the-construct-x-x-y-mean/34707750#34707750 – Michał Perłakowski May 23 '16 at 18:50
@Gothdo The construct is fine as long as you know the pitfalls. Not using it would show a lack of understanding in many cases just like always using `===` for nothing. – plalx May 23 '16 at 21:33
@plalx Well, always using `===` is considered a good practice. – Michał Perłakowski May 23 '16 at 21:37

How can I stop pass by reference an object stored in prototype?

2 Answers2