How to make uglify and grunt index all imports and generate one single file

I have just started using grunt and I want it to use combine all files and uglify them.
But my issues is that it combines and uglifys, but it doesn’t remove import statements. (I’m using uglify and concat)

What I want –

// File.js
import something from './something.js';
something.someFunction("hello world");

and

// something.js
export default {
   someFunction: function(msg){console.log(msg)}
}

to

// all.js
var something = {
  someFunction: function(msg){
     console.log(msg)
  }
}
something.someFunction("hello world");

Compressing is not an issue.