unsure about the intricacies of typescript modules

I have a module file named 'class.ts' that exports a default class MyClass:

// class.ts
export default class MyClass {}
module.exports = MyClass // for importing in node.js withous require('./module').default

When I import this in Node.js, it works fine:

// class-user.js
const Class = require('./class')
const a = new Class() // This is working as expected

However, when I try to use this in TypeScript:

// class-user.ts
import Class from './class'
// The variable 'Class' becomes undefined

// But if I do:

import * as Class from './class'
const a = new Class()
// 'a' is an instance of the Class, but I get an error:
// [ts] Cannot use 'new' with an expression whose type lacks a call or construct signature.

Answer №1

The issue lies within this section:

module.exports = MyClass

This is causing a conflict with your default export.

To resolve this, update your class.ts file to the following:

// class.ts
class MyClass {}
export = MyClass

After making this change, you can use it in the following way:

// class-user.ts
import * as Class from './class'
const obj = new Class()

Note: Avoid using both default and export = in the same module.

Answer №2

When you utilize the syntax import * as Class from './class', what you're essentially doing is instructing the import statement to bring in all exported bindings from the module and map them to the variable Class within your current code file. Therefore, in your specific scenario, the correct way to reference the actual class would be Class.Class because you have used * to map it to Class. The revised version of the code in your example should look like this:

const a = new Class.Class()

For more information on how imports work in JavaScript, you can refer to: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import

Since your objective is simply to use the Class, a more appropriate approach (as you have already discovered) would be to write the following code:

import Class from './class'

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