JSFiddle - React, Tailwind, and code Playground

HTML

<div id="pageMiddle">
    <div id="left_window">
        <div id="project_description" name="project_description" contentEditable="true">Please enter project description...</div>
        <center>
            <button id="save" onclick="save_description()">Save</button>
        </center>
    </div>
</div>

JavaScript

function ajaxObj(meth, url) {
    var x = new XMLHttpRequest();
    x.open(meth, url, true);
    x.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    return x;
}

function ajaxReturn(x) {
    if (x.readyState == 4 && x.status == 200) {
        return true;
    }
}

function _(x) {
    return document.getElementById(x);
}

document.getElementById('save').onclick = function () {
    var des = _("project_description").innerHTML;
    var ajax = ajaxObj("POST", "overview_page.php");
    //ajax.onreadystatechange = function() sorry this one shouldn't be here
    ajax.send("des=" + des);
}