typescript interface syntax for prototyping multidimensional array?

Question

I am trying to add some extension methods for a 2 dimensional array using typescript.

For a 1 dimensional Array the syntax is easy: e.g.

interface Array<T> {
    randomize();  
}
Array.prototype.randomize = function () {
    this.sort(() => (Math.round(Math.random()) - 0.5));
}

I was hoping I could do something similar with a 2 dimensional array, but the following does not work:

interface Array<Array<T>> {
    test();
}

Is it possible in Typescript to prototye on a 2 dimensional array?

Ryan Cavanaugh · Accepted Answer · 2015-02-05 08:53:19Z

1

There isn't any type system mechanism for this. Fundamentally, at runtime, Array.prototype either has a randomize function or it doesn't. You could write a standalone function that had a constraint, though:

function flatten<T extends Array<any>>(arr: T[]): T {
    return null; // TODO implement
}

var x: string[][] = /* ... */;
var y = flatten(x); // y: string[]
var z = flatten(y); // error

As an aside, you should not use that randomize function in earnest. Many sorting algorithms depend on transitivity of ordering (A > B, B > C implies A > C) or stability (A > B implies A > B), which your function does not preserve. This is at best going to be non-uniform and at worst might crash some runtimes.

answered Feb 5, 2015 at 8:53

Ryan Cavanaugh

223k59 gold badges280 silver badges235 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

shelbypereira Over a year ago

not sure I understand "at runtime Array.prototype either has a randomize or it doesn't". The following javascript code works to add the extension method to Array: Array.prototype.randomize = function () { this.sort(function () { return (Math.round(Math.random()) - 0.5); }); }; My issue is that I am unable to do something similar for the 2 dimensional case (using typescript). I am definitely able to use my randomize extension method in the 1d case. NOTE: thanks for comment on randomize, actually this was just a lame example not the focus, I should just have called the method test().

shelbypereira Over a year ago

Actally I should add that in Visual studio 2013 in my typeiscript for the 1D case, I see the warning "Extending prototype of native object "Array" may have unexpected side effects", not sure what these side effects may be...

Collectives™ on Stack Overflow

typescript interface syntax for prototyping multidimensional array?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related