Any way to create a Object that extends Array?

Question

I have created a lexer in javascript, and where im now using an array to describe a range of items, i now see the use of having my own Range object so i can properly distinguish an "array" and a "range array" in such a way that it reads nicely.

So is there any way i can create a hugely cross browser compatible sublcass of the Array object?

Or would a better/simpler approach just using array as is, and for "range arrays" i just tag the array with a property of my own choosing?

something like:

var myRange = [1,2,3];
myrange.isRangeObj = true;

//i would then use if(myRange.isRangeObj) to do specific range operations.
//However i still think myRange instanceof Range reads better

Why do you need to check that at all? You shouldn't have a non-rangy value in the myRange variable. — Bergi
– Bergi, Commented Feb 21, 2013 at 11:06
Yes but i don't have any custom logic, i just want to distinguish a range array and a normal array, later there will be other different array types. Mainly i want to be able to use the same functions as present in the Array object, and also be able to distinguish it as an object of type Range — netbrain
– netbrain, Commented Feb 21, 2013 at 11:07
No. Read how ECMAScript 5 still does not allow to subclass an array — Bergi
– Bergi, Commented Feb 21, 2013 at 11:33

Jefferson Henrique C. Soares · Accepted Answer · 2013-02-21 11:40:36Z

1

You can use this:

Array.prototype.isRangeObj = false;

So all the arrays created by you will have the property isRangeObj

answered Feb 21, 2013 at 11:40

Jefferson Henrique C. Soares

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2 Comments

netbrain Over a year ago

do i need to add it to prototype? would it not suffice to add it to a single instance of array? var arr = []; arr.isRangeObj = false. That way i dont mess with the global scope of array.

Jefferson Henrique C. Soares Over a year ago

Well, I don't really need add it to prototype, it's like you said, I can add only to a single instance, but other instances of Array will return undefined for isRangeObj, so depends of the case, if undefined is enough, so it's better add it to a single instance.

Eric Leschinski · Accepted Answer · 2015-05-29 16:02:37Z

1

Use composition in javascript to create an Object that extends Array:

function Range(arr) {
  this.arr = arr;
}

var myRange = new Range([1, 2, 3]);

if (myRange instanceof Range) {
    doSomethingWithRange(myRange.arr);
}

edited May 29, 2015 at 16:02

Eric Leschinski

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answered Feb 21, 2013 at 11:24

Seiya

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1 Comment

netbrain Over a year ago

I guess that is one solution.

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