Sending data via AJAX using URLSearchParams in JavaScript

It is often not very convenient to manually form a Query String. It is more handy to do this through URLSearchParams:

button.addEventListener('click', function() { let searchParams = new URLSearchParams(); searchParams.set('num1', '1'); searchParams.set('num2', '2'); let promise = fetch('/handler/', { method: 'post', body: searchParams, }); });

The client has a div, a button, and three inputs. Numbers are entered into the inputs. By clicking the button send the entered numbers to a server. Let the server find the sum of sent numbers and return it back. Write result in the div.