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JavaScript JavaScript and the DOM (Retiring) Making Changes to the DOM Getting and Setting Text with textContent and innerHTML

Posted by Amy Tomey
Amy Tomey
12,847 Points

app.js:6 Uncaught TypeError: Cannot set property 'textContent' of null at HTMLButtonElement.<anonymous> (app.js:6)

I cannot find the error in the code that is causing the problem. It MUST be a tiny little thing...

<!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 class="description">Things that are purple:</p>
    <input type="text" class="description">
    <button class="description">Change list description</button>
    <ul>
      <li>grapes</li>
      <li>amethyst</li>
      <li>lavender</li>
      <li>plums</li>
    </ul>
    <script src="app.js"></script>
  </body>
</html>

And the JavaScript:

const input = document.querySelector ('input');
const p = document.querySelector ('description');
const button = document.querySelector ('button');

button.addEventListener ('click', ()=> {
    p.textContent = input.value + ':';
})

Thanks in advance!

2 Answers

Jennifer Nordell
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STAFF
.a{fill-rule:evenodd;}techdegree
Jennifer Nordell
Treehouse Teacher
Jennifer Nordell
.a{fill-rule:evenodd;}techdegree
Jennifer Nordell
Treehouse Teacher

Hi there, Amy Tomey! You are correct. It is a tiny little thing. When picking by a class name in a querySelector() it must be preceded by a . or full stop/period.

You have this:

const p = document.querySelector ('description');

But you should have:

const p = document.querySelector('p.description');  // Note the p. before the description because you're picking the paragraph with a class of "description"

Hope this helps! :sparkles:

Blake Larson
Blake Larson
13,014 Points
Blake Larson
Blake Larson
13,014 Points

You have all three of your elements you are grabbing with the same description class name.

<!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 class="description">Things that are purple:</p>
    <input type="text" class="input">
    <button class="button">Change list description</button>
    <ul>
      <li>grapes</li>
      <li>amethyst</li>
      <li>lavender</li>
      <li>plums</li>
    </ul>
    <script src="app.js"></script>
  </body>
</html>

And just a period before the class name in the selector.

const input = document.querySelector ('.input');
const p = document.querySelector ('.description');
const button = document.querySelector ('.button');

button.addEventListener ('click', ()=> {
    p.textContent = input.value + ':';
})