Hook into all AJAX calls

ajax-hook.js

/* =================== jQuery ===================== */
$(document).ajaxSend(function() {
  alert("Triggered ajaxSend hook.");
});

$('#clickBtn').click(function() {
  $.getJSON("https://crossorigin.me/https://api.darksky.net/forecast/037352c0951701a563b624359ea6111f/42.3601,-71.0589", function(json) {
    console.log("JSON Data:", json);
  });
});


/* =================== Vanilla JS ===================== */
var open = window.XMLHttpRequest.prototype.open,
  send = window.XMLHttpRequest.prototype.send; 

function sendReplacement(data) { 
  if(this.onreadystatechange) { 
    this._onreadystatechange = this.onreadystatechange;
  }
  this.onreadystatechange = onReadyStateChangeReplacement
  
  alert("Triggered XHR hook");
  
  return send.apply(this, arguments);
}

function onReadyStateChangeReplacement() {
  if(this._onreadystatechange) {
    return this._onreadystatechange.apply(this, arguments);
  }
}
 
window.XMLHttpRequest.prototype.send = sendReplacement;