JSFiddle - React, Tailwind, and code Playground

JavaScript

var defer, promise;

defer = $.Deferred( function ( defer ) {
    setTimeout( defer.resolve, 2000 );
});

promise = defer.promise();

defer.then( function () {
    console.log( 'defer.then() works.' );
});

promise.then( function () {
    console.log( 'promise.then() works.' );
});

$.when( defer ).then( function () {
    console.log( '$.when( defer ) works.' );
});

$.when( promise ).then( function () {
    console.log( '$.when( promise ) works.' );
});