JSFiddle - React, Tailwind, and code Playground

JavaScript

var f1 = function() {
    return $.Deferred(function(dfd) {
        dfd.resolve('123 from f1');
    }).promise();
};

var f2 = function() {
    return $.Deferred(function(dfd) {
        dfd.reject('456 from f2');
    }).promise();
};

$.when(f1(), f2())
    .then(function(f1Val, f2Val) {
        alert('success! f1, f2: ' + JSON.stringify([f1Val, f2Val]));
    })
    .fail(function(f1Val, f2Val) {
        alert('fail!    f1, f2: ' + JSON.stringify([f1Val, f2Val]));
    });