Having trouble loading the .php file with my Ajax request

Attempting to retrieve data from the postcode.php file and display it in a #postcodeList div, but encountering issues as nothing happens. Upon inspecting the postcode.php file, it seems to be outputting all the correct information.

var loadicecream = document.getElementById("iceCreams");
loadicecream.addEventListener("click", iceAjax, false);

function iceAjax() {
    var xmlhttp;
    if (window.XMLHttpRequest) {
      xmlhttp = new XMLHttpRequest();
    }
    else {
      xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }

    xmlhttp.open("POST","ice-cream-list.php",true);
    xmlhttp.send();

    document.getElementById("ice-cream-list").innerHTML = xmlhttp.responseText;
}
javascriptajax

Answer №1

It's important to ensure that your query executes asynchronously (using the third parameter in the open function) and then reads the value synchronously afterward. Attempting to read the value before the query has been sent will result in it always being empty.

You have two options: run the load synchronously or set the xmlhttp.onreadystatechange to a function that handles the loaded state. The preferred method is asynchronous loading to prevent blocking the user from using the page while data is being retrieved.

Here is a quick example that only covers the success case:

var xmlhttp;
if (window.XMLHttpRequest) {
  xmlhttp = new XMLHttpRequest();
}
else {
  xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}

xmlhttp.onreadystatechange = function() 
{
    if (xmlhttp.readyState == 4 && xmlhttp.status == 200)
    {
        document.getElementById("postcodeList").innerHTML = xmlhttp.responseText;
    }
}

xmlhttp.open("POST", "postcode.php", true);
xmlhttp.send();

Make sure to refer to the documentation for onreadystatechange, especially when handling timeouts or errors to inform the user if something goes wrong.

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