118 lines
4.2 KiB
Markdown
118 lines
4.2 KiB
Markdown
---
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id: 587d7fae367417b2b2512be4
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title: Access the JSON Data from an API
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challengeType: 6
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forumTopicId: 301499
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---
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## Description
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<section id='description'>
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In the previous challenge, you saw how to get JSON data from the freeCodeCamp Cat Photo API.
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Now you'll take a closer look at the returned data to better understand the JSON format. Recall some notation in JavaScript:
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<blockquote>[ ] -> Square brackets represent an array<br>{ } -> Curly brackets represent an object<br>" " -> Double quotes represent a string. They are also used for key names in JSON</blockquote>
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Understanding the structure of the data that an API returns is important because it influences how you retrieve the values you need.
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On the right, click the "Get Message" button to load the freeCodeCamp Cat Photo API JSON into the HTML.
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The first and last character you see in the JSON data are square brackets <code>[ ]</code>. This means that the returned data is an array. The second character in the JSON data is a curly <code>{</code> bracket, which starts an object. Looking closely, you can see that there are three separate objects. The JSON data is an array of three objects, where each object contains information about a cat photo.
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You learned earlier that objects contain "key-value pairs" that are separated by commas. In the Cat Photo example, the first object has <code>"id":0</code> where "id" is a key and 0 is its corresponding value. Similarly, there are keys for "imageLink", "altText", and "codeNames". Each cat photo object has these same keys, but with different values.
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Another interesting "key-value pair" in the first object is <code>"codeNames":["Juggernaut","Mrs. Wallace","ButterCup"]</code>. Here "codeNames" is the key and its value is an array of three strings. It's possible to have arrays of objects as well as a key with an array as a value.
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Remember how to access data in arrays and objects. Arrays use bracket notation to access a specific index of an item. Objects use either bracket or dot notation to access the value of a given property. Here's an example that prints the "altText" of the first cat photo - note that the parsed JSON data in the editor is saved in a variable called <code>json</code>:
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```js
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console.log(json[0].altText);
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// Prints "A white cat wearing a green helmet shaped melon on its head."
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```
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</section>
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## Instructions
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<section id='instructions'>
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For the cat with the "id" of 2, print to the console the second value in the <code>codeNames</code> array. You should use bracket and dot notation on the object (which is saved in the variable <code>json</code>) to access the value.
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: Your code should use bracket and dot notation to access the proper code name, and print "Loki" to the console.
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testString: assert(code.match(/console\s*\.\s*log\s*\(\s*json\s*\[2\]\s*(\.\s*codeNames|\[\s*('|`|")codeNames\2\s*\])\s*\[\s*1\s*\]\s*\)/g));
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='html-seed'>
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```html
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<script>
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document.addEventListener('DOMContentLoaded',function(){
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document.getElementById('getMessage').onclick=function(){
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req=new XMLHttpRequest();
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req.open("GET",'/json/cats.json',true);
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req.send();
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req.onload=function(){
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json=JSON.parse(req.responseText);
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document.getElementsByClassName('message')[0].innerHTML=JSON.stringify(json);
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// Add your code below this line
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// Add your code above this line
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};
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};
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});
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</script>
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<style>
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body {
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text-align: center;
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font-family: "Helvetica", sans-serif;
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}
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h1 {
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font-size: 2em;
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font-weight: bold;
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}
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.box {
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border-radius: 5px;
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background-color: #eee;
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padding: 20px 5px;
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}
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button {
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color: white;
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background-color: #4791d0;
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border-radius: 5px;
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border: 1px solid #4791d0;
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padding: 5px 10px 8px 10px;
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}
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button:hover {
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background-color: #0F5897;
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border: 1px solid #0F5897;
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}
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</style>
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<h1>Cat Photo Finder</h1>
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<p class="message">
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The message will go here
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</p>
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<p>
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<button id="getMessage">
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Get Message
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</button>
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</p>
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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