[ JS ] Generators and Maps

🔴  Generators

 

const friends = ["Jeong", "Seung", "Ryong", "Hello", "World"];

function* friendTeller() {
  for (const friend of friends) {
    yield friend;
  }
}

const friendLooper = friendTeller();

> friendLooper.next()
// { value: "Jeong", done: false }
> friendLooper.next()
// { value: "Sueng", done: false }
> friendLooper.next()
// { value: "Ryong", done: false }
> friendLooper.next()
// { value: "Hello", done: false }
> friendLooper.next()
// { value: "World", done: false }
> friendLooper.next()
// { value: undefined, done: true }

 

🟠  Proxies

 

const userObj = {
  username: "ryong",
  age: 28,
  password: 1234
};

const userFilter = {
  get: (target, prop, receiver) => {
    return prop === "password" ? `${"*".repeat(5)}` : target[prop];
  },
  set: () => {
    console.log("Somebody wrote something");
  },
  deleteProperty: (target, prop) => {
    if (prop === "password") {
      return;
    } else {
      target[prop] = "DELETED";
    }
  }
};

const filteredUser = new Proxy(userObj, userFilter);

> filteredUser
// { username: "ryong", age: 28, password: 1234 }

> delete filteredUser.password
// false

> delete filteredUser.username
// { username: "DELETED", age: 28, password: 1234 }