How access the whole array object into array.prototype

Question

I'd like to write some like this :

Array.prototype.copy(obj_or_array) {
    if (obj_or_array instanceof Array)
    this.array = this.concat ( obj_or_array.slice());
    else    
    for(var key in obj_or_array) {this.push(obj_or_array[key]);}    
}

'this.array' does not exist but I'd like to have it. Any idea ? Is it impossible ?

Is this a typo? `obj instanceof Array` should be `obj_or_array instanceof Array` — vaso123, Jan 14 '15 at 11:08
Don't use this method to copy objects too as it's on the Array prototype. — Andy, Jan 14 '15 at 11:15
@Andy ??? I dont understand you >lolka_bolka: yes, edited & fixed — civiltomain, Jan 14 '15 at 11:17
@Alnitak The purpose is to have an auto function to clone or copy array or object — civiltomain, Jan 14 '15 at 11:18
Don't have attach a function to clone an object to the Array prototype. You should attach that to the Object prototype. — Andy, Jan 14 '15 at 11:21
Also, such a function should probably be a static method on `Object` rather than something that attempts to mutate the current `this` (the latter often being hard or even impossible) — Alnitak, Jan 14 '15 at 11:22

score 0 · Answer 1 · edited May 23 '17 at 10:33

Here's the simplest way to clone an array using the method in your question:

if (!('copy' in Array.prototype)) {
  Array.prototype.copy = function() {
    return this.slice(0);
  }
}

var arr = [1, 2, 3, 4];
var arr2 = arr.copy();

And if your objects are always going to be simple (ie they don't have any methods), you could use something like this:

if (!('copy' in Object.prototype)) {
  Object.prototype.copy = function() {
    return JSON.parse(JSON.stringify(this));
  }
}

var obj = { name: 'andy' };
var obj2 = obj.copy();

DEMO

score -1 · Answer 2 · answered Jan 14 '15 at 11:27

-1

Something like this?

//Error checking and other stuff omitted this is only an EXAMPLE of an IDEA :)
Array.prototype.loadData = function (a)
{
    if(a instanceof Array)
      for(var i =0; i<a.length; i++) 
          this.push(a[i]);

    else if(a instanceof Object)
      for(var i in a) 
          this.push(a[i]);
}

answered Jan 14 '15 at 11:27

Cipi

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Yes, this is what I have. I'd like (but I think it is impossible to access to the array itself to play with map or concat... this.array = this.array.concat(a) (but 'this.array' does not exist) – civiltomain Jan 14 '15 at 11:52
Correct, `this.array` does not exist, `this` is the actual array, not `this.array`. How exactly do you want to "play" with that "map"? If you want to add/remove items you will still have to use push or other methods to change that array's state. – Cipi Jan 14 '15 at 13:25
I'd like a way to make the job using only one line. From outside you can use Array = AnotherArray.slice() or Array1 =Array1,cancat(Array2( or Arra1 = Array2.map(a_Function...) . The problem is 'How to access to the 'arrayitself' inside the prototype'. The keyword 'this' can be used to use push, etc. But I can't find a way to access to the 'arrayitself' if it'd exis... – civiltomain Jan 14 '15 at 15:30

How access the whole array object into array.prototype

2 Answers2