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JavaScript JavaScript and the DOM Getting a Handle on the DOM Select by Tag Name

Posted by Rafael Singer
Rafael Singer
Courses Plus Student 13,161 Points

Keep getting error message "Cannot read property '1' of null"

Trying to assign variable listItems to the HTML collection of all list items containing the tag <u1>

app.js 
// Complete the challenge by writing JavaScript below
const colors = ["#C2272D", "#F8931F", "#FFFF01", "#009245", "#0193D9", "#0C04ED", "#612F90"];
let listItems = document.getElementsByTagName("ul");

for ( let i = 0; i < colors.length; i++ ) {
  listItems[i].style.color = colors[i];    
}
index.html 
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>JavaScript and the DOM</title>
  </head>
  <body>
    <h1>My List</h1>
    <ul>
      <li>This should be red</li>
      <li>This should be orange</li>
      <li>This should be yellow</li>
      <li>This should be green</li>
      <li>This should be blue</li>
      <li>This should be indigo</li>
      <li>This should be violet</li>
    </ul>
    <script src="app.js"></script>
  </body>
</html>

1 Answer

martinjones1
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
martinjones1
Front End Web Development Techdegree Graduate 44,819 Points
martinjones1
.a{fill-rule:evenodd;}techdegree seal-36
martinjones1
Front End Web Development Techdegree Graduate 44,819 Points

Very close, but the main reason for this error, is that you are only selecting the UL element.

For the UL element, there is only one of them on the page, if you click the preview/refresh button you will see that all of the list items turn red, the first color in the colors array [0]. When it loops over to the colors array to apply the next color, it will not work since it does not exist.

listItems[1].style.color = colors[1];

Instead you need to be selecting the LI elements as below:

// Complete the challenge by writing JavaScript below
const colors = ["#C2272D", "#F8931F", "#FFFF01", "#009245", "#0193D9", "#0C04ED", "#612F90"];
let listItems = document.getElementsByTagName('li');

for ( let i = 0; i < colors.length; i++ ) {
  listItems[i].style.color = colors[i];    
}