Monsters! ES5 to ES6

allTheMonsters.js

function Store(location, monsters){
  this.title = "Monsters"
  this.monsters = monsters || []
  this.location = location
}

Store.prototype.add = function (name) {
  this.monsters.push(new Monster(name));
}

Store.prototype.remove = function (id) {
  id = parseInt(id);
  this.monsters = this.monsters.filter(function (m) {
    return m.id !== id;
  });
}

Store.prototype.find = function (id) {
  id = parseInt(id);
  return this.monsters.find(function (m) {
    return m.id === id;
  });
}


function Monster(name, level) {
  this.name = name;
  this.id = Date.now();
  this.level = level || 1;
}

Monster.prototype.levelUp = function () {
  this.level++;
};

Monster.prototype.levelDown = function () {
  if (this.level > 1) {
    this.level--;
  }
};

Monster.prototype.toHTML = function () {
  return ("<article class='monster-list-item' id=" + this.id + ">" +
      "<h2>" + this.name + "</h2>" +
      "<p class='monster-level'>Level <span class='monster-level-number'>" + this.level + "</span></p>" +
      "<div class='monster-controls'>" +
      "<button class='monster-levelup'>Level Up</button>" +
      "<button class='monster-leveldown'>Level Down</button>" +
      "<button class='monster-delete'>Delete</button>" +
      "</div></article>");
};