Edit in JSFiddle

function showIP(obj) {
    document.getElementById("ip").innerHTML = obj.ip;
    console.log(obj)
}
var url = "http://ip.jsontest.com/?callback=showIP"
var script = document.createElement('script');
script.setAttribute('src', url);
document.getElementsByTagName('head')[0].appendChild(script);

<div id="ip"></div>