At the heart of JavaScript’s asynchronous connection-handling are “promises,” which provide a new way of scheduling how your code will work with JavaScript APIs and functions.

By default, JavaScript is single-threaded, so you can only run one script at a time. With Promises, developers get a standardized way to make asynchronous calls in their code.

An update to tiny "is-promise" library impacted millions of JavaScript projects. Written by Catalin Cimpanu, Contributor April 26, 2020 at 8:19 a.m. PT techrepublic cheat sheet ...