Javascript DOM HTML Document querySelectorAll() Method update by class name

Introduction

Set the background color of all elements in the document with class="example":

Click the button to change the background color of all elements with class="example".

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<!DOCTYPE html>
<html>
<head>
<style>
.example {/*from w  w  w. j a  v a2  s .c o  m*/
  border: 1px solid black;
  margin: 5px;
}
</style>
</head>
<body>

<div class="example">
A div with class="example"
</div>

<div class="example">
Another div with class="example"
</div>

<p class="example">This is a p element with class="example".</p>

<p>This is a <span class="example">span</span> element with class="example" inside another p element.</p>

<button class="example" onclick="myFunction()">Test</button>

<script>
function myFunction() {
  var x = document.querySelectorAll(".example");
  var i;
  for (i = 0; i < x.length; i++) {
    x[i].style.backgroundColor = "red";
  }
}
</script>

</body>
</html>



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