Cannot import module from .ts file – Javascript

I’ve built reactJS projects before, but this time I just need to be able to run a command from the command line so I thought I’d use node for the task. However I’m stuck on importing functions from other files.

I have got this in my main.ts:

import testFunction from './testFunction.js'

async function main() {
    console.log('Node Start Project')
    console.log(testFunction('bobby'))
}

(async () => {
    await main()
})();

And in my package.json:

{
  "name": "testnode",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "main": "node main.ts"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "typescript": "^5.0.4"
  },
  "dependencies": {
    "clarifai-nodejs-grpc": "^8.0.0",
    "dotenv": "^16.0.3",
    "sjcl": "^1.0.8"
  }
}

and in my tsconfig.json:

{
  "compilerOptions": {
    "module": "commonjs",
    "esModuleInterop": true,
    "target": "es6",
    "moduleResolution": "node",
    "sourceMap": true,
    "outDir": "dist"
  },
  "lib": ["es2015"]
}

I want to be able to use Typescript. The testFunction file contains as follows:

    export default function testFunction(name: string): string {
        return 'Hello ' + name
    }

But the error I keep getting is:

(node:12492) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
(Use `node --trace-warnings ...` to show where the warning was created)
/Users/bridgeman/Projects/testnode/main.ts:3
import testFunction from './testFunction.js'

Things I have tried:

• Adding "type":"module" to my package.json file
• Renaming main.ts to main.mjs
• Renaming testfunction.ts to testfunction.mjs
• Using require instead of import: const testFunction = require('./testfunction.ts') (This works, but I can’t use typescript in my function then, I get the error SyntaxError: Unexpected token ':' in the function params)

Please help, I just want to import the function and get on with my project.