JSFiddle - React, Tailwind, and code Playground

JavaScript

function ajax(data, callback) {
    function prepareData(obj) {
        if (!obj) obj = {};
        let data = Object.keys(obj).map(key => {
            let v = obj[key];
            let val = v instanceof Date ? v.getTime() / 1000 : v;
            return [key, val].join('=');
        }).join('&');
        return encodeURI(data);
    }
    var queryString = prepareData(data);
    var request = new XMLHttpRequest();
    request.open('GET', '/exemplo?' + queryString, true);
    request.onload = function() {
        if (request.status >= 200 && request.status < 400) {
            callback(JSON.parse(request.responseText));
        }
    };
    request.send();
}

var data = {foo: 'bar'};
ajax(data, function(res) {
    console.log('Resposta do servidor:', res);
});