nurl/public/javascripts/shorten.js

$('#btn-shorten').on('click', function(){
  $.ajax({
    url: '/api/v1/shorten',
    type: 'POST',
    dataType: 'JSON',
    data: {url: $('#url-field').val()},
    success: function(data){
        const $link = $('#link');
        const resultHTML = `<a class="result" href="${data.shortUrl}">${data.shortUrl}</a>`;
        $link.html(resultHTML);
        $link.hide().fadeIn('slow');
    }
  });

});

(function($) {
    $.extend($.fn, {
        fadeIn: function(ms) {
            if(typeof(ms) === 'undefined') ms = 500;

            $(this).css({ display: 'block', opacity: 0 }).animate({ opacity: 1 }, ms);

            return this;
        },

        fadeOut: function(ms)
        {
            if(typeof(ms) === 'undefined') ms = 500;

            $(this).css({ opacity: 1 }).animate({ opacity: 0 }, ms, 'linear', function() {
                $(this).css('display', 'none');
            });

            return this;
        }
    });
})(Zepto);