TypeScript: augmenting built-in types

Question

how does one augment one of the 'built-in' types? eg Array?

In JS, I'd do something like

Array.prototype.shuffle = function () { ... };

what's the equivalent in TypeScript?

Bill Ticehurst · Accepted Answer · 2012-10-03 04:23:54Z

19

Types are 'open ended' in TypeScript, so you can just write:

interface Array {
  shuffle: () => any; // <-- Whatever signature you want.
}

And then the type is expanded to include the new function (and you can assign a function matching the signature to it).

Note however that extending the built-in types (those in lib.d.ts - such as Array) has an issue currently in the language service, as it caches those internally for perf reasons. Do the workaround I wrote-up at http://typescript.codeplex.com/workitem/4 to extend the built-in types without errors in the language service in VS.

answered Oct 3, 2012 at 4:23

Bill Ticehurst

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3 Comments

Jasper Blues Over a year ago

Can we have the link to the work-around updated pls?

Heretic Monkey Over a year ago

Or just typed into the answer where it should be?

M Miller Over a year ago

Hey all, found the answer on the WayBack Machine! web.archive.org/web/20180115225023/http://…

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