[javascript] How do I include a JavaScript script file in Angular and call a function from that script?

Refer the scripts inside the angular-cli.json (angular.json when using angular 6+) file.

"scripts": [
    "../path" 
 ];

then add in typings.d.ts (create this file in src if it does not already exist)

declare var variableName:any;

Import it in your file as

import * as variable from 'variableName';