JSFiddle - React, Tailwind, and code Playground

JavaScript

// prepare the XHR object
$.ajax({
    beforeSend: function(){
        // right before firing off the request, create a global object that includes the request send time
        window.startTime = new Date();
    },
    
    // send the request to the root URI of this host
    url: '/',
    
    success: function(){
        // once the request comes back, record the end time
        window.endTime = new Date();
        
        // take the difference, which will yield a number in milliseconds, and print it out
        document.write(window.endTime - window.startTime + " ms");
    }
})