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:

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

Задание 1

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.