How to replace jQuery.ajax() with vanilla JavaScript in WordPress

In an effort to remove all jQuery dependency from one of my plugins, I decided to turn all jQuery.ajax() requests into vanilla JavaScript requests. Turns out it’s pretty simple.

Here’s the original request, before:

jQuery.ajax({
    type: 'post',
    url: ipAjaxVar.ajaxurl,
    data: 'action=imagepress-like&nonce=' + ipAjaxVar.nonce + '&imagepress_like=&post_id=' + pid,
    success: function (count) {
        if (count.indexOf('already') !== -1) {
            var lecount = count.replace('already', '');
            if (lecount === '0') {
                lecount = ipAjaxVar.likelabel;
            }
            like.removeClass('liked');
            like.html('<svg class="lnr lnr-heart"><use xlink:href="#lnr-heart"></use></svg> ' + lecount);
        } else {
            count = ipAjaxVar.unlikelabel;
            like.addClass('liked');
            like.html('<svg class="lnr lnr-heart"><use xlink:href="#lnr-heart"></use></svg> ' + count);
        }
    }
});

And here’s the vanilla JavaScript request, after:

var request = new XMLHttpRequest();

request.open('POST', ipAjaxVar.ajaxurl, true);
request.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
request.onload = function () {
    if (this.status >= 200 && this.status < 400) {
        if (this.response.indexOf('already') !== -1) {
            if (this.response.replace('already', '') === '0') {
                likeLabel = ipAjaxVar.likelabel;
            }
            like.classList.remove('liked');
            like.innerHTML = '<svg class="lnr lnr-heart"><use xlink:href="#lnr-heart"></use></svg> ' + likeLabel;
        } else {
            likeLabel = ipAjaxVar.unlikelabel;
            like.classList.add('liked');
            like.innerHTML = '<svg class="lnr lnr-heart"><use xlink:href="#lnr-heart"></use></svg> ' + likeLabel;
        }
    } else {
        // Response error
    }
};
request.onerror = function() {
    // Connection error
};
request.send('action=imagepress-like&nonce=' + ipAjaxVar.nonce + '&imagepress_like=&post_id=' + pid);

Tested and working.

Read more about it here (POST requests using JavaScript) and here (using XMLHttpRequest).

Find more JavaScript tutorials, code snippets and samples here or more jQuery tutorials, code snippets and samples here.