The ':root Selector' is used to select the root element.
Just remember, the root element is always the <html> element.
Let us simplify with the below example.
<html> <head> <title> My First Programme </title> </head> <body> <h1> JQuery </h1> <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> <script src = "https://cdnjs.cloudflare.com/ajax/libs/JQUERY/3.3.1/jquery.min.js"> </script> <script> $('button').click( function() { $(':root').text("All the elements got replaced") }); </script> </body> </html>
So, if you see the above output, on button click, all the contents of the HTML page got replaced with 'All the elements got replaced'.
And this happened with the ':root' element selector.
$('button').click( function() { $(':root').text("All the elements got replaced") });
The moment the button is clicked, JQuery statement gets triggered.
$(':root').text("All the elements got replaced")
And replaces all the contents of the HTML page with 'All the elements got replaced'.