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Inspect the JSON from the response payload

Seeing the response from curl or Postman is cool, but how do you make use of the JSON data? With most API documentation, you don’t need to show how to make use of JSON data. You assume that developers will use their front-end development skills to parse through the data and display it appropriately in their apps. However, to better understand how developers will access the data, we’ll go through a brief tutorial to display the REST response on a web page.

Activity: Make an API request on a web page

For this activity, you’ll use JavaScript to display the API response on a web page. Specifically, you’ll use some auto-generated jQuery code from Postman to create the AJAX request. You’ll get the wind speed from the response and print it to the page.

  1. In an editor such as Sublime Text, create a new HTML file called weather.html and insert the following boilerplate code:

    <html>
       <meta charset="UTF-8">
       <head>
          <title>Sample page</title>
          <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
          <script>
          POSTMAN CODE GOES HERE
          </script>
       </head>
       <body>
          <h1>Sample Page</h1>
          wind speed: <span id="windSpeed"></span>
       </body>
    </html>
    
  2. Assuming you completed the exercises in the Postman tutorial to configure a request, go back into Postman.
  3. In Postman, click the Code link (below the Save button) and go to JavaScript - jQuery:

    Copying JavaScript code from Postman
    Copying JavaScript code from Postman
  4. Copy the Postman code above and insert it into the POSTMAN CODE GOES HERE place in your weather.html file.
  5. Directly below console.log(response);, add these two lines:

    var content = response.wind.speed;
    $("#windSpeed").append(content);
    
  6. Your final code should look as follows:

    <html>
       <meta charset="UTF-8">
       <head>
          <title>Sample page</title>
          <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
          <script>
          var settings = {
            "url": "https://api.openweathermap.org/data/2.5/weather?zip=95050&units=imperial&appid=fd4698c940c6d1da602a70ac34f0b147",
            "method": "GET",
            "timeout": 0,
          };
    
          $.ajax(settings).done(function (response) {
            console.log(response);
            var content = response.wind.speed;
            $("#windSpeed").append(content);
          });
    
          </script>
       </head>
       <body>
          <h1>Sample Page</h1>
          wind speed: <span id="windSpeed"></span>
       </body>
    </html>
    

    What is this code doing? In a nutshell, when ajax (a jQuery function) retrieves the response from the API, it assigns the response to response. A variable called content is created and set it equal to response.wind.speed (dot notation is used to access this value). jQuery’s append method inserts content after an element called #windSpeedon the page. (I realize this is an extremely abbreviated explanation, but explaining JavaScript is beyond the scope of this course. In general, you can learn more by reading about the jQuery.ajax() function.)

  7. Start Chrome and open the JavaScript Console.

    To open the JavaScript Console, on Chrome on a Mac, go to View > Developer > Javascript Console; on Windows, click the menu button (vertical ellipses) and go to More tools > Developer tools. Then click the Console tab.

  8. In Chrome, press Cmd+O (Mac) or Ctrl + O (Windows) and select your weather.html file.

    The weather response should be logged to the JavaScript Console (due to the console.log(response) code in the request). If you expand the object returned to the console, it will look as follows:

    JSON payload from weather API logged to console

    You can view the file here: weather-plain.html.

The AJAX method from jQuery

In this section, I’ll explain a bit more about the ajax function you used earlier. This information probably isn’t essential for documenting REST APIs, but it’s good to understand. In the code, here’s the ajax script:

<script>
   var settings = {
     "async": true,
     "crossDomain": true,
     "url": "https://api.openweathermap.org/data/2.5/weather?zip=95050&appid=fd4698c940c6d1da602a70ac34f0b147&units=imperial",
     "method": "GET"
   }

   $.ajax(settings).done(function (response) {
     console.log(response);
   });
</script>

If you’re working with JavaScript and APIs, the ajax method from jQuery can be helpful with code samples. This ajax method takes one argument: settings.

$.ajax(settings)

The settings argument is an object that contains a variety of key-value pairs.

var settings = {
}

Each of the allowed key-value pairs is defined in jQuery’s ajax documentation.

Some important values are the url, which is the URI or endpoint you are submitting the request to. Another value is headers, which allows you to include custom headers in the request.

Look at the code sample you created. The settings variable is passed in as the argument to the ajax method. jQuery makes the request to the HTTP URL asynchronously, which means it won’t hang up your computer while you wait for the response. You can continue using your application while the request executes.

You get the response by calling the method done.

$.ajax(settings).done(function (response) {
})

In the earlier code sample, done contains an anonymous function (a function without a name) that executes when done is called. The response object from the ajax call is assigned to the done method’s argument, which in this case is response. (You can name the argument whatever you want.)

You can then access the values from the response object using object notation. In this example, the response is just logged to the console.

If you’re new to JavaScript, this is likely a bit fuzzy right now. If so, don’t worry — code becomes clearer the more you use it.

Notice how difficult it is to explain code? This is one of the challenges of developer documentation. Fortunately, you wouldn’t need to explain much from standard programming languages like JavaScript. But you might need to explain how to work with your API in different languages. I cover this topic in more depth in Code samples and tutorials.

Logging responses to the console

The line of code that logged the response to the console was simply this:

console.log(response);

Logging responses to the console can be a useful way to test whether an API response is working (it’s also helpful for debugging or troubleshooting your code). The console collapses each object inside an expandable section. You can inspect the payload in the console to see if contains the values you expect (without printing values to the page).

Inspect the payload

Inspect the payload by expanding each of the sections returned in the JSON console object. Based on the information here, what’s the forecast for today?

I realize the page is blank and unexciting. In the next section, Access and print a specific JSON value, we’ll pull out some values and print them to the page.

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