Django. JS in admin panel for checking letters count.

admin.py

class SomeModelAdmin(admin.ModelAdmin):
    class Media:
        js = ['path/to/script.js']

script.js

/**
 * Created by Developer on 15.09.2017.
 */
(function ($) {
    $(document).ready(function ($) {

        function chars_check_count(text_field) {
            text_field.keyup(function (event) {
                var max_length = $(this).attr('maxlength');

                var charsCurrent = $(this).val().length;
                var spanChars = $(this).next('.help');

                if (charsCurrent >= max_length){
                    spanChars.css('color', 'red').text(charsCurrent + '/' + max_length)
                        .append("<span> characters</span>");
                }
                else
                {
                    spanChars.css('color', 'green').text(charsCurrent + '/' + max_length)
                        .append("<span> characters</span>");
                }
            })
        }

        $('input[type=text]').each(function(){
            chars_check_count($(this))
        });

    });
})(django.jQuery);