TypeScript Array of Callbacks

Question

How would you declare an array of callbacks in TypeScript?

A single callback looks like this:

var callback:(param:string)=>void = function(param:string) {};

So an array of callbacks should look like this:

var callback:(param:string)=>void[] = [];

However, that creates ambiguity, since I could mean an array of callbacks, or a single callback which returns an array of voids.

In the TypeScript playground, it thinks it is an array of voids. So, my next though was to wrap it in parentheses:

var callback:((param:string)=>void)[] = [];

But that doesn't work either.

Any other ideas?

Ryan Cavanaugh · Accepted Answer · 2013-03-27 22:30:04Z

18

You'll need to use the full type literal syntax form, like so:

var callback:{(param:string): void;}[] = [];

This is sort of ugly; if you like you can make a name for it first:

interface fn {
    (param: string): void;
}
var callback2: fn[] = [];

answered Mar 27, 2013 at 22:30

Ryan Cavanaugh

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2 Comments

Cool. That's much better than the any[] I temporarily had in there. Thanks. =)

Typescript gets so weird... sometimes you just want to store an array of callback listeners and you end up with this gibberish in your codebase.