just-import

If you are getting the following error, this simple library can help:

Error [ERR_REQUIRE_ESM]: require() of ES Module ... from ... not supported.
Instead change the require of ... in ... to a dynamic import() which is available in all CommonJS modules.

You are likely getting this error because you are transpiling ESM or TypeScript to CommonJS, and no matter what, the emitted code uses require to import libraries.

Libraries written in ESM style cannot be required'd. They must use the native Node import function.

This library does nothing except wrap the import function in justImport, isolating it from your compile process.

Here is how you can fix your problem using split-chars as an example:

import { justImport } from 'just-import'

async function splitChars (input: string) {
  const splitChars = await justImport<Iterable<string>>('split-chars')
  return splitChars.default(input)
}

or in TypeScript

import { justImport } from 'just-import'

type SplitChars = {
  default: (input: string) => Iterable<string>
}

async function splitChars (input: string): Promise<Iterable<string>> {
  const { default:splitChars } = await justImport<SplitChars>('split-chars')
  return await splitChars(input)
}

Please see EXAMPLES for more examples.

Can't the offending module be imported just like any other so the function doesn't have to be async?

Sadly, no. Since import returns a promise, so too mush justImport. require is synchronous, but again, the module can't me imported using require.

If you're not going to use the module right away, there is an unsafe way to import it:

import { justImport } from 'just-import'

let splitChars = null
justImport('split-chars').then(mod => {
  splitChars = mod.default
})

function myCode () {
  return splitChars('🍍+🍕=😋')
}

or in TypeScript

import { justImport } from 'just-import'

let splitChars: (input: string) => Iterable<string> = null
justImport('split-chars').then(mod => {
  splitChars = mod.default
})