Access function defines in JavaScript file from TypeScript file

I don't believe that you can call a function from a script added via .angular-cli.json, although you can implement IIFEs that way. Normal usage is for external libraries (bootstrap.js, collapse, animations and the like) as they get added as <script> tags in the index.html.

Rather than adding it to your angular-cli.json, it's easier to import it in your components

1. Give MyFile a .ts extension to avoid having to pass the --allowJs flag. E.g., MyFile.ts
2. Make sure to export your functions. If you have several, you might put them in a class and make them static (but that's a different question). Here's what I did:

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// myfile.ts
export const myFunction = () => {
  console.log('hello');
};

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3. Import the script into the desired component via import { myFunction } from '../assets/js/myFunction'

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import { Component, OnInit } from '@angular/core';  
import { myFunction} from '../assets/js/myfile';

@Component({  
  selector: 'app-root',  
  templateUrl: './app.component.html',  
  styleUrls: ['./app.component.css']  
})  


export class AppComponent implements OnInit {
  title = 'app';

  ngOnInit() {
    myFunction();
  }
}

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