The ':header Selector' is used to select all the header elements, i.e. <h1>, <h2> e.t.c.
Let us simplify with the below example.
<html>
<head>
<title> My First Programme </title>
</head>
<body>
<h1> First Heading </h1>
<h2> Second Heading </h2>
<h3> Third Heading </h3>
<div class = "newClass">
<p class = "para1"> First Paragraph </p>
<p class = "para2"> Second Paragraph </p>
<p class = "para3"> Third Paragraph </p>
</div>
<button> Click me </button>
<h4> Fourth Heading </h4>
<script src = "https://ajax.googleapis.com/ajax/libs/jquery/3.7.1/jquery.min.js"> </script>
<script>
$('button').click( function() {
$(':header').text("All the header elements got replaced")
});
</script>
</body>
</html>
So, if you see the above code. We can see that there are four headers.
<h1> First Heading </h1> <h2> Second Heading </h2> <h3> Third Heading </h3> <h4> Fourth Heading </h4>
And on button click, the contents of all the header elements got replaced.
And this happened with the ':header' element selector.
$('button').click( function() {
$(':header').text("All the header elements got replaced")
});The moment the button is clicked, JQuery statement gets triggered.
$(':header').text("All the header elements got replaced")And replaces all the header elements with 'All the header elements got replaced'.