JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>

JavaScript

var species = "human";
var chr      = 7;
var fromPos = 139424940;
var toPos   = 141784100;
var cback = "cback";
var prefix  = "http://beta.rest.ensembl.org/feature/region/"

var url = prefix + species + "/" + chr + ":" + fromPos + "-" + toPos + ".jsonp?feature=gene;callback=" + cback;

console.log(url);
$.ajax({
    url           : url,
    dataType      : 'jsonp',
    contentType   : "application/json",
    jsonpCallback : 'cback',
    crossDomain   : true,
    jsonp         : false,
    success       : function(json) {console.log("RESP: " + json)}, 
    error         : function(error) {console.log("ERROR: " + error.message)}
});