Import with 'require' cannot be used when targeting ECMAScript 6 or higher

问题

In VS2019 16.2.1, I created a new project using the Basic Azure Node.js Express 4 Application with TypeScript Template.

I can build and run the application.

However, in app.ts, if I hover over the line

import debug = require('debug');

I see a tooltip

Import with 'require' cannot be used when targeting ECMAScript 6 or higher

Here is tsconfig.json

  "compilerOptions": {
    "module": "commonjs",
    "target": "es6",
    "lib": ["es6"],
    "sourceMap": true
  },
  "exclude": [
    "node_modules"
  ]
}

Why do I see this message and what should I do about it?

[Update]

I tried changing the first line to

import debug from 'debug';

then I get build errors

app.ts(1,8): error TS1259: Module '"C:/Users/kirst/source/repos/ExpressApp1/ExpressApp1/node_modules/@types/debug/index"' can only be default-imported using the 'esModuleInterop' flag

[Update] The warning dissappears when I suspend Resharper Ultimate.

If I switch to ES5 and try

import from 'debug'  ( with or without a semicolon )

I see an error

can only be default-imported using the 'esModuleInterop' flag

If I use

import * as debug from 'debug'

It works

回答1:

Instead of using

import debug = require('debug');

you should use

import * as debug from 'debug' // Import everything from that module
// OR
import debug from 'debug' // Import only the class 'debug' from that module

// Depends on the module

This is the new Syntax in ES6

_{(Read more)}

If you want to use the old style of importing modules you can set "target" to "ES5" in your tsconfig.json file.