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javascripthtmldomdom-eventsdom-manipulation

Iterate elements and toggle using classList in javascript

Conditions:

  1. Please use javascript and classList property to invert which elements have .highlight class.
  2. Basically iterate over all the <li> elements and toggle the class of .highlight. on each one.
  3. You should not alter anything in HTML and CSS.

Your result should be like this!

/* app.js */
let list =  document.querySelector('li');

list.classList.add('');
/* index.css */
/*No need to touch anything in this file:*/
li {
  background-color: #B10DC9;
}

.highlight {
  background-color: #7FDBFF;
}
<!-- index.html -->
<!DOCTYPE html>
<head>
    <title>ClasList</title>
</head>
<body>
<link rel="stylesheet" type="text/css" href="index.css">
    <!--LEAVE THIS FILE ALONE!-->
    <ul>
        <li>Hello</li>
        <li class="highlight">Hello</li>
        <li>Hello</li>
        <li>Hello</li>
        <li class="highlight">Hello</li>
        <li>Hello</li>
    </ul>
    <script src="app.js"></script>
</body>
</html>

Solution

  • The following solution removes the .highlight class style from the <li> if the .highlight class style is applied to the <li>. If the .highlight class style is not applied to the <li> element, the .highlight class style is added to the <li> element.

    Method-1

    /* The querySelectorAll() method is used to select all <li> elements. */
let list = document.querySelectorAll('li');
var listArray = [...list];

/* Each <li> element is checked using the forEach() method. */
listArray.forEach(element => {
  /* Is the ".highlight" class style applied to the <li> element? */
  if(element.classList.contains("highlight")) {
    /* Remove the ".highlight" class style from the <li> element. */
    element.classList.remove("highlight");
  }
  else {
    /* Add the class style ".highlight" to the <li> element. */
    element.classList.add("highlight");
  }
});
    li {
  background-color: #B10DC9;
}

.highlight {
  background-color: #7FDBFF;
}
    <!DOCTYPE html>
<head>
  <title>ClasList</title>
  <link rel="stylesheet" type="text/css" href="index.css">
</head>
<body>
  <ul>
      <li>Hello</li>
      <li class="highlight">Hello</li>
      <li>Hello</li>
      <li>Hello</li>
      <li class="highlight">Hello</li>
      <li>Hello</li>
  </ul>
  <script src="app.js"></script>
</body>
</html>

    Method-2

    /* The querySelectorAll() method is used to select all <li> elements. */
let list = document.querySelectorAll('li');

window.addEventListener('load', (event) => {
  for(let i = 0 ; i < list.length ; ++i) {
    if(list[i].classList.contains("highlight")) 
      list[i].classList.remove("highlight");
    else 
      list[i].classList.add("highlight");
  }
});
    li {
  background-color: #B10DC9;
}

.highlight {
  background-color: #7FDBFF;
}
    <!DOCTYPE html>
<head>
  <title>ClasList</title>
  <link rel="stylesheet" type="text/css" href="index.css">
</head>
<body>
  <ul>
      <li>Hello</li>
      <li class="highlight">Hello</li>
      <li>Hello</li>
      <li>Hello</li>
      <li class="highlight">Hello</li>
      <li>Hello</li>
  </ul>
  <script src="app.js"></script>
</body>
</html>