I'm having some trouble creating a complete application using an API, specifically the Forecast.io weather api. For simplicity, I've put my JS directly in my HTML page. For this basic version, I would be happy just to have this show something. Let's say I wanted current temperature (currently -> temperature). Also, I'm not sure if "?callback?" is always recommended for all RESTful APIs.
<!DOCTYPE html>
<html>
    <body>  
    <p id="weather">Here's the weather:<p>
    <button onclick="b()">Submit</button>
        <script>
        function b(){
            var apiKey = '<private>';
            var url = 'https://api.forecast.io/forecast/';
            var lati = 0;
            var longi = 0;
            var data;
            $.getJSON(url + apiKey + "/" + lati + "," + longi + "?callback=?", function(data) {
              $('#weather').innerHTML('and the weather is: ' + data[4].temperature);
            });
        }
        </script>
    </body>
</html>
 
     
    