What is async/await in JavaScript? From Callback Hell to Promises, React, and Next.js, explained with real code

When building web pages or apps, you will often encounter the two terms async and await in JavaScript. These are terms ...
Ars Technica

JS: premature method return due to asynchronous function call

var a, async = function(f) { setTimeout(function() { var r = 'step 2'; f(r); }, 1); }, myFunc = function() { a = 'step 1'; async(function(r) { a = r; // should reset ...