Saving a file in a UWP web context

I recently developed a universal application for Windows 10 with UWP web context (so JavaScript and HTML) and I would like to save a text file. It works well on a browser (Chrome, Firefox, Edge,...) but not in the application. Can someone help me? :) Thank you in advance!

Here is the code responsible for saving the text file.

function saveTextAsFile(fileName) {
var source = input.value.replace(/\n/g, "\r\n");
var fileUrl = window.URL.createObjectURL(new Blob([source], {type:"text/plain"}));
var downloadLink = createDownloadLink(fileUrl, fileName);

document.body.appendChild(downloadLink);
downloadLink.click();
document.body.removeChild(downloadLink);}