Dynamic Function Call for Prototype Functions

Question

I have to make a bunch of .prototype declarations within a function and would like to add some dynamism to reduce the size of my code.

Here is some pseudo code for what I need to do:

window.myClass = function(){
  var object_type = getObjectType();
  if (object_type === 'NodeList')
  {
     NodeList.prototype.func_name = function(){
         //some code 
     }
  }

  if (object_type === 'HTMLCollection')
  {
     HTMLCollection.prototype.func_name = function(){
         //the same code again 
     }
  }
}

I would like to change this so I can make these declarations dynamic, kind of like this:

window.myClass = function(){
  var object_type = getObjectType();
  object_type.prototype.func_name = function(){
     //some code
  }
}

Is this possible?

EDIT

I forgot to mention that I would love to keep all my functions within the scope of window.myClass

What you should probably do is define these functions elsewhere, then assign them within the if conditions if (object_type === 'HTMLCollection') { HTMLCollection.prototype.func_name = yourFunction; } — that'll greatly improve readability. — royhowie
– royhowie, Commented May 29, 2015 at 6:46

Denys Séguret · Accepted Answer · 2015-05-29 06:55:51Z

1

In your case you can simply do

window[object_type].prototype[func_name] = function(){...

But be careful that you seem to be engaged in modifying objects you don't own. There's probably a better possible design for your application.

edited May 29, 2015 at 6:55

answered May 29, 2015 at 6:45

Denys Séguret

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1 Comment

ObiHill Over a year ago

Thanks. I would prefer not to break scope from my initial object. I'm not sure if this is possible.

user663031 · Accepted Answer · 2015-05-29 07:36:00Z

0

Without going into details about what are you trying to accomplish or whether it's a good idea or there are better ways to do it, just based on your posted code, all you need to do is define "some code" as a funtion and assign it to whatever you want:

window.myClass = function(){
  function someCode() { /* some code */ }

  var object_type = getObjectType();
  if (object_type === 'NodeList')
  {
     NodeList.prototype.func_name = someCode;
  }

  if (object_type === 'HTMLCollection')
  {
     HTMLCollection.prototype.func_name = someCode;
  }
}

But you don't really need the if statement, because you can just do

window.myClass = function(){
  function someCode() { /* some code */ }

  var object_type = getObjectType();
  window[object_type].prototype.func_name = someCode;
}

answered May 29, 2015 at 7:36

user663031

4 Comments

ObiHill Over a year ago

Thanks for this. I would not be comfortable with extending the window object (as your second code block suggests). Is there a way I can use this same bracket notation for things within the scope of my original object e.g. [object_type].prototype.func_name?

user663031 Over a year ago

You're not extending the window object. You're adding a function to the prototype of something which is already on the window object.

ObiHill Over a year ago

So does that mean the code is encapsulated and there isn't any chance of collisions?

user663031 Over a year ago

There is a chance of collisions if someone else adds the same method to the prototype of the same DOM class.

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