Fetch details from JSON string return by URL using JavaScript

<input type="button" id="demo" value="Parse URL" onclick="ParseURL()" />
<script type="text/javascript">
    function httpGet(theUrl) {
        var xmlHttp = new XMLHttpRequest();
        xmlHttp.open("GET", theUrl, false);
        xmlHttp.send(null);
        return xmlHttp.responseText;
    }
    function ParseURL() {
        var json = httpGet("http://api.ipinfodb.com/v3/ip-city/?key=3b8fbb8b954ae5daad70021283f3fd56b&ip=933.207.145.193&format=json");
        var response = eval('(' + json + ')');
        alert("IP Address: " + response.ipAddress + "\nStatus Message: " + response.statusMessage);
    }
</script>