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JavaScript

Posted by blueskyispink
blueskyispink
2,997 Points

Why class selector for two elements works, but selection using tags + descendant combinator does not?

Hello all,

Whilst doing the challenge I had to select the images from the <footer> and save it onto footerImages.

I tried to use:

footerImages = document.querySelectorAll('footer a');

but it threw out an error. Consequently, just using the class selector .social-icon worked!

Whilst I understand why the latter worked, why did 'footer a' not work? I think that is a pretty granular selection of the elements. Furthermore, I checked in the console and it did select have a NodeList of 2 elements. I can't fully grasp that aspect, so wasn't sure it was indicative of anything.

Help would be appreciated!

P.S. Any suggestions to learn about the selector hierarchies in a bit more detail?

The html code:

index.html 
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Nick Pettit | Designer</title>
    <link rel="stylesheet" href="css/normalize.css">
    <link href='http://fonts.googleapis.com/css?family=Changa+One|Open+Sans:400italic,700italic,400,700,800' rel='stylesheet' type='text/css'>
    <link rel="stylesheet" href="css/main.css">
    <link rel="stylesheet" href="css/responsive.css">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
  </head>
  <body>
    <header>
      <a href="index.html" id="logo">
        <h1>Nick Pettit</h1>
        <h2>Designer</h2>
      </a>
      <nav>
        <ul>
          <li><a href="index.html" class="selected">Portfolio</a></li>
          <li><a href="about.html">About</a></li>
          <li><a href="contact.html">Contact</a></li>
        </ul>
      </nav>
    </header>
    <div id="wrapper">
      <section>
        <ul id="gallery">
          <li>
            <a href="img/numbers-01.jpg">
              <img src="img/numbers-01.jpg" alt="">
              <p>Experimentation with color and texture.</p>
            </a>
          </li>
          <li>
            <a href="img/numbers-02.jpg">
              <img src="img/numbers-02.jpg" alt="">
              <p>Playing with blending modes in Photoshop.</p>
            </a>
          </li>
        </ul>
      </section>
      <footer>
        <a href="http://twitter.com/nickrp"><img src="img/twitter-wrap.png" alt="Twitter Logo" class="social-icon"></a>
        <a href="http://facebook.com/nickpettit"><img src="img/facebook-wrap.png" alt="Facebook Logo" class="social-icon"></a>
        <p>&copy; 2016 Nick Pettit.</p>
      </footer>
    </div>
  <script src="app.js"></script>
  </body>
</html>

2 Answers

Liam Clarke
Liam Clarke
19,938 Points

Hello

Your answer is correct with both solutions you tried. This is more of a Treehouse compiler thing when testing you have the correct answer.

As for which one is better, it is always better to target your element with exact specificity to avoid bugs.

footerImages = document.querySelectorAll('footer a');

This will not only get the direct anchor children, but if you had any nested even furher, it will also get them too so you could potentially get unwanted results.

There are ways around this, such as the :scope pseudo but for ease, if you can target by class or ID, it will give more expected results in multiple different scenarios.

Good Luck

blueskyispink
blueskyispink
2,997 Points
blueskyispink
blueskyispink
2,997 Points

Thanks so much Liam! It is good to know, and it makes sense if the granularity is simply described by a unique id to that element.