Concept

Here's my solution using ES6

Very much inline with @Bergi's response, this is the "template" I use when creating imports that need parameters passed for class declarations. This is used on an isomorphic framework I'm writing, so will work with a transpiler in the browser and in node.js (I use Babel with Webpack):

./MyClass.js

export default (Param1, Param2) => class MyClass {
    constructor(){
        console.log( Param1 );
    }
}

./main.js

import MyClassFactory from './MyClass.js';

let MyClass = MyClassFactory('foo', 'bar');

let myInstance = new MyClass();

The above will output foo in a console

EDIT

Real World Example

For a real world example, I'm using this to pass in a namespace for accessing other classes and instances within a framework. Because we're simply creating a function and passing the object in as an argument, we can use it with our class declaration likeso:

export default (UIFramework) => class MyView extends UIFramework.Type.View {
    getModels() {
        // ...
        UIFramework.Models.getModelsForView( this._models );
        // ...
    }
}

The importation is a bit more complicated and automagical in my case given that it's an entire framework, but essentially this is what is happening:

// ...
getView( viewName ){
    //...
    const ViewFactory = require(viewFileLoc);
    const View = ViewFactory(this);
    return new View();
}
// ...

I hope this helps!

You can also use npm package called esm which allows you to use ES6 modules in Node.js. It needs no configuration. With esm you will be able to use export/import in your JavaScript files.

Run the following command on your terminal

yarn add esm

or

npm install esm

After that, you need to require this package when starting your server with node. For example if your node server runs index.js file, you would use the command

node -r esm index.js

You can also add it in your package.json file like this

{
  "name": "My-app",
  "version": "1.0.0",
  "description": "Some Hack",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node -r esm index.js"
  },

}

Then run this command from the terminal to start your node server

npm start

Check this link for more details.

The issue, as you said is that import is currently only being supported globally via Node. If you want to quickly import code on the client side, and jQuery is an option, then you can use:

$.getScript( "ajax/test.js" )
.done(function( script, textStatus ) {
    console.log( textStatus );
})
.fail(function( jqxhr, settings, exception ) {
    $( "div.log" ).text( "Triggered ajaxError handler." );
});

This will load and execute the JavaScript code from the server. The callback done is called when the script has finished downloading, but not necessarily completed execution.

For more info, you can look at the official reference