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JavaScript JavaScript and the DOM (Retiring) Getting a Handle on the DOM Selecting Elements with the Same Class Name

Posted by Matt Roberts
Matt Roberts
5,173 Points

The elements are not changing purple or red respectively and I don't know why

I'm not seeing any errors in the console so hard to debug

app.js

const myList = document.getElementsByTagName('li');

for (let i = 0; i < myList.length; i += 1) { myList[i].style.color = 'purple'; }

const errorNotPurple = document.getElementsByClassName('error-not-purple');

for (let i = 0; i < errorNotPurple.length; i += 1) { errorNotPurple[i].style.color = 'red'; }

html <!DOCTYPE html> <html> <head> <title>JavaScript and the DOM</title> <link rel="stylesheet" href="css/style.css"> </head> <body> <h1 id="myHeading">JavaScript and the DOM</h1> <p>Making a web page interactive</p> <input type="text" id="myTextInput1"> <button id="myButton">change headline colour</button> <input type="text" id="myTextInput2"> <button id="myButton2">change button colour</button> <script src="app.js"></script> <p>Things that are purple:</p> <ul> <li>grapes</li> <li class="error-not-purple"> oranges</li> <li>amethyst</li> <li class="error-not-purple"> firetruck</li> <li>lavender</li> <li class="error-not-purple"> computer </li> <li>plums</li> </ul>

</body> </html>

4 Answers

Carlos Chavez
Carlos Chavez
5,691 Points
Carlos Chavez
Carlos Chavez
5,691 Points

I found that the position of your script element was not at the end of you html file. This also caused problem for me before.

<!DOCTYPE html> 
<html> 
  <head> 
    <title>JavaScript and the DOM</title> 
    <link rel="stylesheet" href="css/style.css"> 
  </head> 
  <body> 
    <h1 id="myHeading">JavaScript and the DOM</h1> 
    <p>Making a web page interactive</p> 
    <input type="text" id="myTextInput1"> 
    <button id="myButton">change headline colour</button> 
    <input type="text" id="myTextInput2"> 
    <button id="myButton2">change button colour</button> 

    <p>Things that are purple:</p> 
    <ul> 
      <li>grapes</li> 
      <li class="error-not-purple"> oranges</li> 
      <li>amethyst</li> <li class="error-not-purple"> firetruck</li> 
      <li>lavender</li> <li class="error-not-purple"> computer </li> 
      <li>plums</li> 
    </ul>
    <script src="app.js"></script>
  </body> 
</html>

Here's another thread about it: https://teamtreehouse.com/community/how-does-the-order-in-which-you-place-your-html-elements-matter

Alzubair Alshehhi
Alzubair Alshehhi
2,792 Points
Alzubair Alshehhi
Alzubair Alshehhi
2,792 Points

I have copied your code exactly and it worked, maybe you didn't save the code before preview?

HTML

<!DOCTYPE html>
<html>
  <head>
    <title>JavaScript and the DOM</title>
    <link rel="stylesheet" href="css/style.css">
  </head>
  <body>
    <h1 id="myHeading">JavaScript and the DOM</h1>
    <p>Making a web page interactive</p>
    <p>Things that are purple:</p>
    <ul>
        <li>grapes</li>
      <li class="error-not-purple"> oranges</li>
        <li>amethyst</li>
      <li class="error-not-purple"> firetruck</li>
        <li>lavender</li>
      <li class="error-not-purple"> computer </li>
        <li>plums</li>
    </ul>
    <script src="app.js"></script>
  </body>
</html>

app.js

const myList = document.getElementsByTagName('li');

for (let i = 0; i < myList.length; i += 1) {
  myList[i].style.color = 'purple';
}

const errorNotPurple = document.getElementsByClassName('error-not-purple');

for (let i = 0; i < errorNotPurple.length; i += 1) {
  errorNotPurple[i].style.color = 'red'; 
}
Steven Parker
Steven Parker
231,248 Points
Steven Parker
Steven Parker
231,248 Points

Unless I'm overlooking something because the code was posted without formatting, this works fine as-is.

A better way to share code and make your issue easy to replicate is to make a snapshot of your workspace and post the link to it here.

Harinder Singh
Harinder Singh
4,214 Points
Harinder Singh
Harinder Singh
4,214 Points

I fixed it by changing all

<li class="error-not-purple">

to

<li class="errorNotPurple">

so it matches the way we wrote it in app.js