DefinitelyTyped definitions for Express not working

Question

I'm trying to get a Hello World express app running in node with typescript, and the DefinitelyTyped types just appear to be completely ignored.

package.json:

{
    "dependencies": {
        "@types/express": "*",
        "@types/node": "*",
        "express": "*"
    }
}

tsconfig.json:

{
    "compilerOptions": {
        "module": "commonjs",
        "lib": [
            "es2015"
        ],
        "target": "es6",
        "noImplicitAny": true,
        "strictNullChecks": true,
        "noImplicitThis": true,
        "noImplicitReturns": true,
        "moduleResolution": "node",
        "outDir": "dist",
        "baseUrl": "."
    },
    "include": [
        "src/**/*"
    ]
}

src/app.ts:

const express = require('express'); //express is typed "any" because @types/express is apparently ignored
const app = express();
const port = 3000;
app.get('/', (req, res) => res.send('Hello World!')); //Compile error here because implicit any
app.listen(port, () => console.log(`Example app listening on port ${port}!`));

Compile output:

~/tmp/ws-test$ tsc
src/app.ts(5,15): error TS7006: Parameter 'req' implicitly has an 'any' type.
src/app.ts(5,20): error TS7006: Parameter 'res' implicitly has an 'any' type.

I feel like I'm taking crazy pills. What's wrong here?

Juraj, you win, that did it. It seems like those should be identical statements, right? Is there some semantic difference I'm not aware of? — Ben Dilts
i have no type when i use require insteed of new es imports, not sure why but i have never been try to solve, i am always using import... — Juraj Kocan

Bjørn Bråthen Bjørn Bråthen · Accepted Answer · 2019-01-11T18:03:38

In your particular setup, you'll have to do imports in one of two ways:

import express = require('express');

or:

import * as express from 'express';

If you wan't imports like:

import express from 'express';

You can add "allowSyntheticDefaultImports": true to the compilerOptions.

DefinitelyTyped definitions for Express not working

1 Answers