title: Check how many <li> there are in a <ul> with javascript
body: <p>Following my code:</p>
  
  <p>HTML:</p>
  
  <pre><code>&lt;ul id="ul_o"&gt;
  &lt;li&gt;v1&lt;/li&gt;
  &lt;li&gt;v2&lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p>JS:</p>
  
  <pre><code>console.log(document.getElementById("ul_o").getElementsByClassName("LI").length);
  </code></pre>
  
  <p>Why the in the console there are the number 0 instead of 2?</p>