Laravel 5.4 TokenMismatchException Ajax call

I get a TokenMismatchException error only when I submit a form with an ajax call? If I don't use an Ajax call I don't get the error.

What is causing this?

Laravel 5.4

I have this in the head of my app.blade.php:

<meta name="csrf-token" content="">

My ajax.js

$( document ).ready(function() {
    // storing comments
    $('#storeComment').on('submit', function(e) {
        e.preventDefault();

        $.ajax({
            method: 'POST',
            url: '/comments',
            data: {},
            success: function(response){
                console.log(response);
            },
            error: function(jqXHR, textStatus, errorThrown) { 
                console.log(JSON.stringify(jqXHR));
                console.log("AJAX error: " + textStatus + ' : ' + errorThrown);
            }
        });
    });
});

I also use the bootstrap.js that automatically registers the value of the csrf-token meta tag with the Axios HTTP library. As explained in the Laravel documentation.

via Chebli Mohamed