app.js

var database = firebase.database();
var userID = window.location.search.match(/\?id=(.*)/)[1];

$(document).ready(function () {

  $('input').val('');

  database.ref("users/" + userID).once("value")
    .then(function (snapshot) {
      var userInfo = snapshot.val();
    })

  database.ref("users").once("value")
    .then(function (snapshot) {
      snapshot.forEach(function (childSnapshot) {
        var childKey = childSnapshot.key;
        var childData = childSnapshot.val();
        createUsers(childData.email, childKey);
      });
    })

  $('input').keyup(getSearch);

  getGifsFromAPI();

  $('#red-btn').click(getSearch);

  $('#green-btn').click(likedGif);
  $('#favorite').click(() => window.location = "favoritos.html?id=" + userID);

});

let indexOfGif = -1;

//chamando o Hammer.js
const myElement = document.getElementById('card-image');
const mc = new Hammer(myElement);
// listen to events...
mc.on("swipeleft", getSearch);
mc.on("swiperight", likedGif);

function getSearch(event) {
  let searchItem = buscaPalavra();
  if (!searchItem) {
    getGifsFromAPI();
  }
  trazBusca(searchItem);
}

function trazBusca(searchItem) {
  $.ajax({
    type: 'GET',
    url: `http://api.giphy.com/v1/gifs/search?q=${searchItem}&api_key=${keyAPI}&limit=100`,
    success: showGif,
    error: erro
  });
}

function buscaPalavra(){
  return document.getElementById("search").value;
}

function likedGif() {
  getSearch();
  addToFav()
}

function getGifsFromAPI() {
  $.ajax({
    type: 'GET',
    url: `https://api.giphy.com/v1/gifs/search?q=gif&api_key=rc0vl8oEetDnA6wEuyjXXwtGB99EYxSS&limit=100 `,
    success: showGif,
    error: erro
  });
}

function showGif(data) {
  indexOfGif += 1;
  urlImg = data['data'][indexOfGif]['images']['original']['url'];
  $('img').attr('src', urlImg);
  gifTitle = data['data'][indexOfGif]['title'];
  $('#gif-title').html(gifTitle);
  }

function addToFav() {

  return database.ref("favorites/" + userID).push({
    url: urlImg,
    title: gifTitle

  });
}

function erro() {
  console.log('erro');
}