What practice is recommended to check if jQuery’s Ajax function is present and is recognized by the browser, does anyone know?

Question

What practice is recommended to check if jQuery’s Ajax function is present and is recognized by the browser, can anyone say?

// forma 1
if (!$.ajax) {
  alert ('Status xhr: não suporta Ajax');
 return false;
}
// forma 2
if (typeof $.ajax !== 'function') {
  alert ('Status xhr: não suporta Ajax');
 return false;
}

In many of the examples on the Mozilla MDN website the condition for testing functions according to the form 1 and well used, at a glance:

https://developer.mozilla.org/en-US/docs/Web/Guide/AJAX/Getting_Started

Answer 1

Utilize jQuery.support.ajax or $.support.ajax

if (!$.support.ajax) {
    alert("Status xhr: não suporta Ajax");
}

Answer 2

First you can create a variable to make a request ajax any

Dai inside the function you will test the possible browsers , if not accept returns an error

    function ajaxFunction() {
      var xmlHttp;

      try {
       // Firefox, Opera 8.0+, Safari
       xmlHttp=new XMLHttpRequest();
      }
      catch (e) {
        // Internet Explorer
        try  {

           xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");

        }
        catch (e) {
          try {
            xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
          }
          catch (e) {
             alert("Your browser does not support AJAX!");

             return false;
         }

    }

Answer 3

I got the code on http://programmerguru.com/ajax-tutorial/browser-support/

    <script type="text/javascript"> 
      var xmlhttp; 
      function checkAJAXSupport() {
        if (window.XMLHttpRequest) { // Mozilla, Safari, ...
          xmlhttp= new XMLHttpRequest();
          alert("Yes. Your browser must be one among them - Mozilla, Safari, Chrome, Rockmelt, IE 8.0 or above");
        } else if (window.ActiveXObject) { // IE
          try {
            xmlhttp= new ActiveXObject("Msxml2.XMLHTTP");
            alert("Yes. Your browser must be IE");
          } 
          catch (e) {
            try {
              xmlhttp= new ActiveXObject("Microsoft.XMLHTTP");
              alert("Yes. Your browser must be IE");
            } 
            catch (e) {}
          }
        }  if (!xmlhttp) {
          alert("No. Giving up Cannot create an XMLHTTP instance. Your browser is outdated!");
          return false;
        } 
 } 
</script>

Answer 4

You can use When in your request

    $.when( $.ajax ).then(function( data, textStatus, 
      jqXHR ) {
      alert( jqXHR.status ); // Alerts 200
    })
    .catch(function() {
      alert ('Status xhr: não suporta Ajax');
    })