Conversation started Dec 26, 2015 at 17:48.
Mast
Mast
Dec 26, 2015 17:48
@DanPantry:
It's the same as creating an extension method in C# -- you're extending the behaviour of a specific type with a specific functionality. The compatibility issue is moot: if a new function is introduced that does this for you then you just remove your own definition and that's that. Provide unit tests and you will know if a breaking change is introduced which you can act accordingly upon. — Jeroen Vannevel 2 mins ago
On prototyping.
Dan Pantry
Dan Pantry
Dec 26, 2015 18:19
That sounds about right, @Mast.
Except it is more like adding a instance method than an extension method.
Mast
Mast
Why is adding an instance method not an extension?
But basically, it's a good idea here and a bad idea somewhere else?
Now I just need to figure out the difference.
 
1 hour later…
Dan Pantry
Dan Pantry
Dec 26, 2015 19:35
@Mast I'm not sure what you're asking
Mast
Mast
@DanPantry If I understand you correctly you can add methods to a class in two ways, as instance method and as extension method.
Dan Pantry
Dan Pantry
@Mast in javascript?
To a class - no, you can only add methods to a class via a prototype.
you CAN add methods to an INSTANCE
but that is not to a class.
Mast
Mast
Ah, now I get it.
Dan Pantry
Dan Pantry
Here's the difference. 
class Foo {
  instanceMethod() {}
  static classMethod() {}
}
This transpiles to this: 
const Foo = (function() {
  function Foo() {}
  Foo.classMethod = function classMethod() {}
  Foo.prototype.instanceMethod = function instanceMethod() {}
  return Foo;
}());
now if I do new Foo() I'll get an instance of the Foo class. It will have instanceMethod on it - same as any other OOP language
Mast
Mast
Basically you're extending the class but only for that instance.
A kind of overloading.
Dan Pantry
Dan Pantry
Dec 26, 2015 19:40
Er, sort of. What I just showed you was prototypal inheritence.
the other one, the extending one, looks like this. 
var foo = new Foo();
foo.instanceMethod = function instanceMethod() {}
This will override foo.instanceMethod for that specific instance.
Generally speaking, you don't want to do this for obvious reasons
Mast
Mast
So, do the first and not the latter?
Dan Pantry
Dan Pantry
if you're making classes, generally speaking you're sharing behaviour
So yes, use prototypes
If you're not sharing behaviour you probably shouldn't be using classes but object literals instead
Which are just the normal way of creating objects.. 
var foo = {
  function instanceMethod() {}
}
Mast
Mast
And not like I did here:
5
Q: Two-dimensional array, modified one field at a time

MastTitle says it all. I'm basically initializing a two-dimensional array and changing the fields one at a time. It might be a good idea to do this OO. A Grid class seems right, perhaps as a subclass of Array. So far I haven't been able to successfully port it. Pointers would probably be a good idea...

javascript memory-optimization
Array.shoot = function(row, column, array) {
  array[row][column] = "H";
  return array;
}
Dan Pantry
Dan Pantry
Yeah, that doesn't make sense at all
Well, I mean
those are essentially static utility methods
But uh
don't use the namespace Array either
You don't want to be modifying vendor types (like Array, String, Function) etc
for what it is worth, by the way
The latest tends in JS tend to avoid using classes and use more functional concepts instead
Although you definitely want to use classes if you'r ereusing functionality
because attaching things to the prototype chain reduces memory usage
(because functions on the prototype chain are only created once, whereas closures have to be created each time)
In this instance I would use Flambino's first implementation personally :)
Mast
Mast
@DanPantry Right. That's what I learned.
Don't do that.
But prototyping on Strings is perfectly ok?
@DanPantry Yea, that's what I'm thinking.
Dan Pantry
Dan Pantry
Dec 26, 2015 19:56
@Mast No.
Do not modify any vendor type
or their prototypes
Mast
Mast
@DanPantry String.prototype.endsWith
That's what is being suggested.
Dan Pantry
Dan Pantry
@Mast that's because endsWith, I believe, is a method introduced in ES6.
developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
Modifying a vendor type in this case is okay. This is called a shim.
Mast
Mast
> Modifying a vendor type in this case is okay.
> Do not modify any vendor type
At least now I know why it's confusing.
Dan Pantry
Dan Pantry
Okay, i should clarify
Don't modify a vendor type wtih a custom method
endsWith is not a custom method, but it exists in ES6
for backwards cmpatibility purposes, we check whether or notendsWith exists. if it doesn't we shim it
Mast
Mast
Dec 26, 2015 20:21
Right.
 
Conversation ended Dec 26, 2015 at 20:21.