Typescript: how to import a class from a javascript file?

Question

I would like to :

• Import a js file that defines a class: ./myClass/index.js
• Declare the public methods of MyClass somewhere (in index.ts or a specified declaration file, I really don't know how to do it)
• Have a typescript file that exposes the class: index.ts

something like

// index.ts import MyClass from './myClass' // or require, or anything that would work export {MyClass} 

and

// myClass/index.js export default class MyClass { ... } 

This obviously does not work, as the import of ./myClass/index won't find the module.

The thing is, I tried to create a ./myClass/index.d.ts file based on this example, but no matter what, I still have a Error: Cannot find module './myClass/index.js' error at runtime :(

I feel like I miss some typescript basics here but I'm striving to find some clear resources.

Any ideas ?

Answer 1

There is no export default class in JavaScript. What you can do is write your JS file like this. myClass/index.js

"use strict"; class MyClass { hello(name) { console.log(`Hello ${name}`); } } exports.default = MyClass; 

Create a Type definitions for it. myClass/index.d.ts

export default class MyClass { hello(name: string): void; } 

You can then import it into your TypeScript like this.

/// <reference path="./myClass/index.d.ts" /> import MyClass from "./myClass"; const my = new MyClass(); my.hello("Stack Overflow"); 

Answer 2

at the end of the your javascript file , write this

exports.MyClass = MyClass; 

in ts files

import * as IzendaSynergy from './izenda/izenda_ui.js'; 

or

import { IzendaSynergy } from './izenda/izenda_ui.js'; 

in tsconfig.json file

 "allowJs": true