Comments in jQuery are used to create notes about what the code block does and how it works, and can also be used to temporarily prevent code execution.

Any text between the // and the end of the line will be ignored by the browser (will not be executed). Anything on the line before the // will run normally. And anything on lines after the comment will run normally.

$('button').click(function() {
    $('p').hide();
    // $('p').show();
});

document.getElementById('my_output').innerHTML = 'Hello World';

Comments in jQuery can also wrap to multiple lines and anything between the /* and */ will be the comment, including any code that you don’t want the browser to run. This is called “commenting out” code.

/* this is a
a much longer
comment

$('p').hide();
*/

As mentioned above, comments in jQuery can also be used to “comment out” a section of code that you’d like to keep intact for future use, but “turn off” for the time being. By wrapping a comment around the code, it will not be implemented by the browser.

The structure of the comment stays the same, but the comment itself is the code you no longer want the browser to run. In the following, we comment out the original string and replace it with “Hello Universe”.

document.getElementById('my_output').innerHTML = /* 'Hello World' */ 'Hello Universe';