How to add external js file in angular 4?

To add an external js file into Angular 4, follow these steps:

• Refer the scripts inside the angular-cli.json file like this:
  "scripts": [ "../path" ];
• Add this into typings.d.ts :
  declare var variableName:any;
• Import the above onto your js file as:
  import * as variable from 'variableName';