function displayUsers() {

  var request = new XMLHttpRequest();
  request.onreadystatechange = function() {
    if(request.readyState == 4) {
      var text = request.responseText;
      var users = JSON.parse(text);
      // PARCOURIR
      users.forEach(function(user) {
        console.log(user.email);
      });
      // CHERCHER
      var res = users.find(function(user) {
        if(user.email == "bon@bon.com") {
          return true;
        }
        return false;
      });
      console.log(res);
      // TRANSFORMER
      var res2 = users.map(function(user) {
        return user.id;
      });
      console.log(res2);
      // DOM
      document.getElementById('user_container_id').innerHTML = "";
      users.forEach(insertUser);
    }
  }
  request.open('GET', 'list_user.php');
  request.send();
}