I'm having trouble with a jszip configuration

Question

I'm trying to hook up jszip to my Flask/python project running in VS on windows, but JS crashes as soon as I try to import jszip or declare an instance with the 'var JSZip = require("jszip");' call. I've tried both downloading and extracting the zip installer as well as installing with npm. Npm installs with success and node is in the path. The npm seem to create a folder within the 'static' called 'node_modules\jszip' while i've unzipped the one I downloaded to 'scripts\jszip'. When I either add the 'import' declaration or the 'var JSZip = require("jszip");' line, the js function crashes. Same if I only call the top folder 'import JSZip from 'node_modules/jszip'. Without the 'import' nor the 'require' call, the Alert displays. I'm a new to js modules, so it's probably a very basic error but I just cannot spot it. Any help appreciated :-)

import JSZip from 'node_modules/jszip/dist/jszip.js';

function download_zip(arrUrls) {
    alert("1");
    var JSZip = require("jszip");
}