snippets.js

/**
 *
 * @param {} obj object to filter
 * @param  {...any} allowedKeys proporties to keep
 * @returns object with only allowed keys
 */
const filterObj = (obj, ...allowedKeys) => {
  const newObj = {};
  Object.keys(obj).forEach((key) => {
    if (allowedKeys.includes(key)) {
      newObj[key] = obj[key];
    }
  });
  return newObj;
};

const obj1 = {
  name: 'john',
  email: '[email protected]',
  password: 'test123',
  accessType: 'user',
};

console.log(filterObj(obj1, 'name', 'email'));

/* usage of arrow function inside the method */
const birthdayParty = {
  forWho: 'mia',
  friends: ['jonas', 'andrew', 'lara'],
  // function declaration with concise syntax. You shouldn't use arrow function to create method.
  inviteFriends() {
    console.log(`This party for ${this.forWho.toUpperCase()}.`);
    /**
     * In regular functions the this keyword represented the object that called the function, which could be the window, the document, a button or whatever.
     * Arrow function does not have its own bindings to 'this'. It uses enclosing scope's 'this'
     */
    this.friends.forEach((friend) => {
      console.log(`${friend}, are you coming for ${this.forWho}'s party?`);
    });
  },
};
birthdayParty.inviteFriends();