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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
231,269 Points
Steven Parker
Steven Parker
231,269 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.