Edit in JSFiddle

<script>
    function clicked()
    {
        var xhr = new XMLHttpRequest();
        var url = document.getElementById("url").value;
        if(url == ""){alert("Please enter URL"); return;}
        var xhr =  new XMLHttpRequest();
    xhr.open("GET", "https://www.googleapis.com/pagespeedonline/v1/runPagespeed?url="+encodeURIComponent(url)+"&key=AIzaSyBlRIfnn5fH9bfhPbkSOtjLIOeF8WmQtio&strategy=mobile");
    xhr.onload = function(){
        document.getElementById("data").innerHTML = xhr.responseText;
    }
    xhr.send();
    }
</script>
<input type="text" placeholder="Enter webpage URL" id="url" />
<input type="button" value="PageSpeed Data" onclick="clicked();" />
<pre id="data">
    
</pre>