JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">Loading...</div>

JavaScript

//Ajax emulator
$.ajax = function (options) {
    var r = function () {
        return Math.random() * 100;
    };
    var d = $.Deferred();
    d.then(options.success);
    setTimeout(function () {
        d.resolve({
            V1: r(),
            V2: r(),
            V3: r(),
            V4: r()
        });
    }, Math.random() * 10000);
    return d.promise();
};

//Highcharts emulator
$.fn.highcharts = function () {
    var container = this;
    return new (function () {
        this.series = [{
            setData: function (data) {
                container.empty();
                $.each(data, function(i, d) {
                    container.append('<div>X: ' + d.x + ', Y: ' + d.y + '</div>');
                });
            }
        }]
    })();
};

var chart = $('#container').highcharts({
    series: [{
        data: (

        function () {

            //We'll initialize an array of zeroes to set your series up
            var initialData = [];
                //This will eventually be populated with our data
            var ajaxData = [];
            //References to all our requests we'll make
            var ajaxRequests = [];

            y1 = 5,
            y2 = 5,
            y3 = 5,
            y4 = 5;

            function myFunction(x) {
                return $.ajax({
                    type: "GET",
                    url: "/getTest",
                    success: function (data) {
                        console.log("1st 1:", y1, y2, y3, y4);
                        y1 = data.V1;
                        y2 = data.V2;
                        y3 = data.V3;
                        y4 = data.V4;
                        console.log("1st 2:", y1, y2, y3, y4);
                        //Add the returned data to our array in the correct position
                        ajaxData.push({
                            x: x,
                            y: y1
                        });
                    }
                });
            };

           ...