JSFiddle - React, Tailwind, and code Playground

JavaScript

function GetAllFileNames(ms, def) {
    setTimeout(function() {
        console.log('Get all file names');
        def.resolve();
        return 20;
    }, ms);
}

function getfilenames() {

    var def = $.Deferred();

    var result = GetAllFileNames(2000, def);

    return def;
}

getfilenames().then(function() {
    console.log('Got all file names');
});