This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag

Question

I'm trying to make a simple API using typescript and NodeJS but when I run my code I get this error

"This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag."

This is my code: package.json

    {
  "name": "API-Proyecto",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "cors": "^2.8.5",
    "express": "^4.17.1",
    "jsonwebtoken": "^8.5.1"
  },
  "devDependencies": {
    "@types/cors": "^2.8.6",
    "@types/express": "^4.17.6",
    "nodemon": "^2.0.4"
  }
}

Index.ts

    import express from 'express';
import { Request, Response }  from 'express';
import cors from 'cors';

const app = express();

app.use(express.urlencoded({extended: true}));
app.use(express.json);
app.use(cors({origin: true, credentials: true}));

app.get('/api/auth/testing', (req: Request, res: Response) =>{
    res.status(200).json({
        ok : true,
        msg : 'hi from my method'
    });
});

app.listen(3000, () => {console.log('Server running on 3000' )});

tsconfig.json

    {
  "compilerOptions": {
    "target": "es6",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
    "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
    "outDir": "./dist",                        /* Redirect output structure to the directory. */
    "esModuleInterop": true,                  /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
  }
}

Your code is fine. If you are curious on this flag I've created a lesson on it: https://www.youtube.com/watch?v=bx4AjADk6eQ — basarat, Jun 09 '20 at 05:28
Thank you so much! I don't have an idea about the error but your lesson is helpful to learn more — Antonio Labra, Jun 09 '20 at 15:44
I had a similar problem, but I forgot to create de tsconfig.json file. once i generated it, the issue was fixed — innis, Jan 22 '22 at 01:03
This one is missing [Interop Constraints](https://www.typescriptlang.org/tsconfig#Interop_Constraints_6252) — Code with Marty, Jun 29 '22 at 12:22

score 169 · Accepted Answer · edited Jul 29 '21 at 15:53

169

Your code is perfectly fine.

Fix

When you make changes to tsconfig, sometimes you need to restart your IDE or Code Editor

edited Jul 29 '21 at 15:53

Cavdy

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answered Jun 09 '20 at 05:28

basarat

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22

If you are using VSCode, you can run `TypeScript: Reload Project` from the command pallet. – Sean256 Jul 29 '21 at 19:22

score 101 · Answer 2 · answered Dec 20 '20 at 01:04

101

Use:

import * as express from 'express';

answered Dec 20 '20 at 01:04

Ayrton Everton

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I had a similar issue for momentjs in VSCode and your approach resolved my case. – Utku A. Dec 20 '21 at 18:43
This raised a tsserver error on `express()`: `This expression is not callable. Type 'typeof e' has no call signatures. (tsserver 2349)` – manuch100 Jun 20 '23 at 09:46
Maybe you're using a version of the `express` package that doesn't return a function by default, so I recommend either looking in the documentation or trying to find it in their project implementation or doing a debug to see everything that is exported by `express`, because there may be some version that needs to call a function inside the object, which would be something like `express.function()`. – Ayrton Everton Jun 21 '23 at 14:25

score 29 · Answer 3 · answered May 20 '21 at 11:42

29

My problem was that I tried to run tsc as tsc -w index.ts.

However, as said here https://stackoverflow.com/a/33244030/5711655 if you run tsc with a specified input file, it won't use the tsconfig.json in your project directory! So in my case I had to use tsc -w.

answered May 20 '21 at 11:42

jeti

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That is so annoying that tsc ignores tsconfig.json when called with a specific file argument. – hlovdal Apr 25 '23 at 12:25

score 17 · Answer 4 · edited Apr 25 '22 at 05:53

17

I fixed similar mistake for yourself. I use project (vite + vue 3 + ts)

added on tsconfig.json->compilerOptions + "moduleResolution": "node".
import moment from "moment" to import * as moment from "moment";

UPD:- and add this setting,

"allowSyntheticDefaultImports": true

and then I can use, import moment from "moment";

edited Apr 25 '22 at 05:53

Anil Nivargi

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answered Apr 15 '22 at 07:53

LOC

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`import * as somelibrary from "somelibrary"` worked for me thanks. – John Yepthomi Aug 21 '22 at 19:42

atleugim · Answer 5 · 2023-04-05T15:27:40.560

12

I was able to solve it by setting the "esModuleInterop" property to true inside the "compilerOptions" object in the tsconfig.json file.

{
  "compilerOptions": {
    "esModuleInterop": true,
    ...
  },
}

edited Apr 05 '23 at 15:27

answered Dec 13 '22 at 16:30

atleugim

121
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helped in my case as well – Alex Kogan Jun 19 '23 at 22:23

score 7 · Answer 6 · edited Jan 08 '22 at 09:39

7

Don't forget to set "moduleResolution": "node" in the tsconfig.json if you are using node.

edited Jan 08 '22 at 09:39

glennsl

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answered Mar 08 '21 at 12:13

TommyTomato

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score 6 · Answer 7 · answered Sep 03 '22 at 14:17

when working with Ts you you need to add a flag on your tsconfig.json file that allow Synthetic Imports as so:

open tsconfig.json
add: { "compilerOptions": { "jsx": "react", "module": "es6", "target": "es6", "moduleResolution": "node", "allowSyntheticDefaultImports": true } }

Hope it helps. Cheers!

score 1 · Answer 8 · answered Jun 12 '20 at 02:37

I was wondering a lot but a friend helped me:

You need to create a command inside of "scripts" part on package.json

Package.json

{
  "name": "api-proyecto",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    **"build-dev": "tsc -w"**
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@types/cors": "^2.8.6",
    "@types/express": "^4.17.6"
  },
  "dependencies": {
    "cors": "^2.8.5",
    "express": "^4.17.1"
  }
}

To run your script you need to type the following line

npm i run build-dev (because it's the name of our command)
Finally in another powershell launch node normally. For Example:

node .\dist\index.js

score 1 · Answer 9 · answered Jan 27 '22 at 21:58

1

FWIW, I found that switching from

import * as blah from 'blah-lib';

To

const blah = require('blah-lib');

Fixed the issue at compile time.

answered Jan 27 '22 at 21:58

Joseph Lust

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this is not a solution since he wants to use esModules style – Careuno Merchan Jun 06 '22 at 19:19

score 1 · Answer 10 · answered Feb 26 '22 at 05:50

1

I solved the problem by compiling the whole file instead of compiling individual files.

Just run the following command to compile the whole file in a go

npx tsc

This should solve your problem

answered Feb 26 '22 at 05:50

citizen4

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It works for me with conjunction with this answer: https://stackoverflow.com/a/74788007/7883681 – Tayan May 10 '23 at 23:21

score 0 · Answer 11 · answered Aug 03 '22 at 18:11

0

After trying all of the above solutions to no avail, I stumbled upon a solution for my case. I don't know why this works but running tsc instead of tsc index.ts or tsc --watch index.ts compiled fine. This error makes no sense to me at all. If someone can enlighten me and other readers of this post, it would be greatly appreciated.

answered Aug 03 '22 at 18:11

Bus42

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This is already explained in an earlier answer to this question: https://stackoverflow.com/a/67619647/224639 – Nev Stokes Oct 18 '22 at 10:06

score 0 · Answer 12 · answered Oct 31 '22 at 11:00

0

I tried everything on this thread and it didn't work. What finally did was swapping tsc for ts-node to compile typescript in the app.

For reference I had this problem in a rushjs monorepo which may have further confused tsc

answered Oct 31 '22 at 11:00

stakolee

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score 0 · Answer 13 · answered May 31 '23 at 12:30

Just like @basarat said rightfully, restarting Typescript can fix this issue. I already included "esModuleInterop": true, in tsconfig.json. I want to add, that you can do this via the Intellij Footer as well. Click on your Typescript version there.

Thanks for the help.

score 0 · Answer 14 · answered Jun 27 '23 at 16:06

I had the same issue with my vscode, the error keeps on popping even with changing the tsconfig.json.

The problem was that tsconfig.json was extending from expo/tsconfig.base and somehow vscode didn't detect it.

{
  "compilerOptions": {
    "baseUrl": ".",
    "paths": {
      "src/*": ["src/*"],
      "static/*": ["static/*"]
    }
  },
  "extends": "expo/tsconfig.base"
}

I just opened this expo/tsconfig.base with right click and then save it to make vscode aware of this.

This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag

14 Answers14

Fix

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