What is the proper way to define a new property for an object within an npm package?

Snippet:

import * as request from 'superagent';

request
    .get('https://***.execute-api.eu-west-1.amazonaws.com/dev/')
    .proxy(this.options.proxy)

Error in TypeScript:

Property 'proxy' is not found on type 'SuperAgentRequest'

Type annotations for the 'request' module:

(alias) namespace request
(alias) const request: request.SuperAgentStatic
import request

My attempt at creating type definitions (which did not resolve the TypeScript error):

declare module superagent {
    interface SuperAgentRequest {
        proxy: any;
    }
}

What mistake could be present in my declaration file?

typescript

Answer №1

One important thing to remember is to always include double quotes around the word superagent when declaring the module.

If you are starting from scratch without any types to enhance, you can create a separate .d.ts file (e.g. globals.d.ts) and add the following code:

declare module "superagent" {
  interface SuperAgentRequest {
    proxy: any;
  }

  export function get(s: string): SuperAgentRequest;
}

After creating this declaration file, you can then import the module in your TypeScript file like this:

import * as request from "superagent";

request
  // The get method returns a request.SuperAgentRequest object
  .get("https://***.execute-api.eu-west-1.amazonaws.com/dev/")
  .proxy(this.options.proxy);

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