JQuery is an actively used library created in 2006.

13Years Old 2,027,659Users 19,868Jobs

Example code from Wikipedia:

$.ajax({
  type: 'POST',
  url: '/process/submit.php',
  data: {
    name : 'John',
    location : 'Boston',
  },
}).done(function(msg) {
  alert('Data Saved: ' + msg);
}).fail(function(xmlHttpRequest, statusText, errorThrown) {
  alert(
    'Your form submission failed.\n\n'
      + 'XML Http Request: ' + JSON.stringify(xmlHttpRequest)
      + ',\nStatus Text: ' + statusText
      + ',\nError Thrown: ' + errorThrown);
});
Edit

Last updated February 11th, 2019