How to Eval with imported Module in ES6 and Webpack

I use Webpack as a package manager and ES6. Looks like an imported module is not correctly evaluated with eval. How to eval a string using the imported Module ?

Code:

In a global scope:

 <script type="text/javascript">
     var tableDefinition = '{ value: "myvalue", myfunction: (v) => { return DateFormat.format(v) }}'; 
 </script>

In my module:

import DateFormat from "~modules/DateFormat"; // a module helper written by me

class GeneriClass {
    constructor() {
        DateFormat.init();
        let columns = eval(tableDefinition); // this code retrieves 'DateFormat' not defined
    }
}

The error on eval is: "'DateFormat' not defined!"