Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript AJAX Basics (retiring) AJAX and APIs Create a callback function

Posted by Megan Markle
Megan Markle
379 Points

Trouble understanding why we put 'weatherReport' as a parameter?

I understand the basics of a parameter, but I'm starting to think I don't. Isn't it later defined when you assign a value to it? That's why I don't understand the concept here. Can anyone explain how it works here?

Thanks

weather.js 
$(document).ready(function() {
  var weatherAPI = 'http://api.openweathermap.org/data/2.5/weather';
  var data = {
    q : "Portland,OR",
    units : "metric"
  };
  function showWeather(weatherReport) {
    $("#temperature").text(weatherReport.main.temp);
  };



});//End
index.html 
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>What's the Weather Like?</title>
  <script src="jquery.js"></script>
  <script src="weather.js"></script>
</head>
<body>
  <div id="main">
    <h1>Current temperature: <span id="temperature"></span>&deg;</h1>
  </div>
</body>
</html>

1 Answer

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

A parameter acts as a placeholder for a value that will be supplied when the function is called.

This code is still incomplete, so it won't "work" as-is. The function is defined, but the code that will use it has not been added yet. Also, since this function will be used as a callback, you will not see where the actual call occurs, but you know from the API description that an argument will be supplied to it at that time.