Extend a namespace from package typings

You can easily extend the 'fullcalendar' or any other TypeScript namespace.

Example: create fullcalendar-extension.d.ts file

/// <reference path="<path-to-typings-dir>/fullcalendar/index.d.ts" />

declare module 'fullcalendar' {

  export interface TimeGrid {

    customField: string;

    customMethod(arg1: number, arg2: boolean): boolean;

    prepareHits();
  }

  namespace customNamespace {

    export interface AnotherTimeGrid {
      customField1: string;
      customField2: boolean;
    }
  }
}

Note: ensure that this file is picked-up by the TypeScript compiler.

Use the newly defined types from the extended module.

// one way
import { TimeGrid } from 'fullcalendar';

const timeGrid: TimeGrid;

// second way
import * as fc from 'fullcalendar';

const timeGrid: fc.TimeGrid;
const anotherTimeGrid: fc.customNamespace.AnotherTimeGrid;

For more info on modules and namespaces you can check TypeScript documentation on Modules and Namespaces and using them together.

Cheers!

We can import a namespace in a non-declaration .ts, and export it again as a extended type:

// custom-fc.ts : enhances declaration of FC namespace
import * as origFC from "fullcalendar";

declare namespace Complimentary {
    class TimeGrid {
        prepareHits(): void;
    }
    let views: any;
}

// apply additional types to origFc and export again
export const FC: (typeof Complimentary & typeof origFC) = origFC as any;

 

// use-fc.ts : consumer of extended declaration
import { FC } from "./custom-fc";

console.log(FC.TimeGrid);
console.log(FC.views);

(This somehow differs from your scenario, in that I'm using @types/ packages and webpack ts-loader, but you should be able to do something similar.)