How to use a compiled TypeScript class in Javascript

Question

Imagine I have this simple TypeScript class, Animal.ts:

export default class Animal {
  constructor(public name : string) { }
}

With this tsconfig.json file:

{
  "compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "strict": true
  },
  "files": [
    "Animal"
  ]
}

How can I use the compiled version of this class (compiled by running tsc) in a javascript file like so:

var Animal = require("./Animal");

var newAnimal = new Animal();

Should I edit something in my tsconfig.json file? The error I get is:

ReferenceError: Animal is not defined

You can have typescript compile javascript files as well using 'allowJs' (in tsconfig.json). That way, you can reference typescript classes from your javascript. — Brian
– Brian, Commented Dec 18, 2017 at 21:42
Since you are using default export, I do believe you have to require it like var Animal = require("./Animal").default <-- note the .default at the end. — CRice
– CRice, Commented Dec 18, 2017 at 21:47
Exporting with export default makes your export an module. It would become new Animal.default('name'). However the error is not reproducible, the Animal is exported as { __esModule: true, default: [Function: Animal] }. — Shane
– Shane, Commented Dec 18, 2017 at 21:47
Yes, sorry I just noticed that. I have been using Babel which also exports it using module.exports = .... You can do const { Animal } = require('./animal');. — Shane
– Shane, Commented Dec 18, 2017 at 22:07

Sergey Yarotskiy · Accepted Answer · 2017-12-19 17:43:23Z

9

As Shane van den Bogaard pointed out, the default keyword in Animal.ts needs to be omitted and :

const { Animal } = require('./Animal');

should be used instead of

var Animal = require('./Animal');

This way we can call the Animal class and initialize an object by using

const { Animal } = require('./Animal');
var newAnimal = new Animal("Clifford");

Sergey Yarotskiy

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answered Dec 18, 2017 at 22:21

Titulum

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