CODEWITHSUNDEEP
typescript
Bart van den Burg
Bart van den Burg

Reputation: 2364

Typescript: add function to momentjs' prototype

I'm trying to add a function to the momentjs prototype. In Javascript, the code was like this:

Object.getPrototypeOf(moment()).isWeekend = function() {
    return this.isoWeekday() >= 6;
};

How do I do this in typescript? I've read that i need to duplicate the interface and and my function to it, but that's not working:

module moment {
    interface Moment {
        isWeekend(): boolean
    }

    Moment.prototype.isWeekend = () => {
        this.isoWeekday() >= 6;
    };
}

Upvotes: 3

Views: 2814

Answers (2)

Bibby Chung
Bibby Chung

Reputation: 166

It's working for me.

import * as moment from 'moment';
declare module 'moment' {
  export interface Moment {
    toTaiwaneseYear(): number;
  }
}

(moment.fn as any).toTaiwaneseYear = function () {
  const _self = this as moment.Moment;
  return _self.year() - 1911;
}

reference:

https://medium.com/my-life/extension-method-in-typescript-66d801488589

Upvotes: 1

Fenton
Fenton

Reputation: 251102

You need to place the actual extension outside of the module, and you need to export the interface...

module moment {
    export interface Moment {
        isWeekend(): boolean
    }
}

(<any>moment).fn.isWeekend = function() {
    this.isoWeekday() >= 6;
};

Upvotes: 2

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