How to import a js file into a TypeScript project?

Question

JavaScript

Let's say we have a config.js file that defines a constructor function:

function ConfigService () {
    this.greeting = function() {console.log('Hello World');}
}

What should the header file look like in order to import without errors?

Answer 1

Describe the library interface in a .d.ts file. Name this file something like global.d.ts and put it in the root of the project (where all the ts files are, usually the /src folder). You can read more here https://basarat.gitbooks.io/typescript/docs/types/... . Here is the complete documentation https://www.typescriptlang.org/docs/handbook/decla... .
The file itself will look something like this:

// global.d.ts
declare function ConfigService();