es6 generators and symbols examples

example_01.js

function* shopping() {
  // stuff on the sidewalk

  // walking down the sidewalk

  // go into the store with cash
  const stuffFromStore = yield 'cash';

  // walking to laundry place
  const cleanClothes = yield 'laundry';

  // walking back home
  return [stuffFromStore, cleanClothes];
}

// stuff in the store
const gen = shopping();
gen.next(); // leaving our house
// walked into the store
// walking up ad down the aisles...
// purchase our stuff
gen.next('groceries'); // leaving the store with groceries
gen.next('clean clothes');

example_02.js

const testingTeam = {
  lead : 'Amanda',
  tester : 'Bill'
};

const engineeringTeam = {
  testingTeam,
  size : 3,
  department : 'Engineering',
  lead : 'Jill',
  manager : 'Alex',
  engineer : 'Dave'
};

function* TestingTeamIterator(team){
  yield team.lead;
  yield team.tester;
}

function* TeamIterator(team) {
  yield team.lead;
  yield team.manager;
  yield team.engineer;
  const testingTeamGenerator = TestingTeamIterator(team.testingTeam);
  yield* testingTeamGenerator; // delegation
}

const names = [];
for(let name of TeamIterator(engineeringTeam)){
  names.push(name);
}

console.log(names);

example_03.js

const testingTeam = {
  lead : 'Amanda',
  tester : 'Bill',

  [Symbol.iterator]: function* () {
    yield this.lead;
    yield this.tester;
  }
};

const engineeringTeam = {
  testingTeam,
  size : 3,
  department : 'Engineering',
  lead : 'Jill',
  manager : 'Alex',
  engineer : 'Dave',

  [Symbol.iterator]: function* () {
    yield this.lead;
    yield this.manager;
    yield this.engineer;
    yield* this.testingTeam;
  }
};

const names = [];
for(let name of engineeringTeam){
  names.push(name);
}

console.log(names);

example_04.js

class Comment {
  constructor(content, children) {
    this.content = content;
    this.children = children;
  }

  *[Symbol.iterator]() {
    yield this.content;
    for(let child of this.children){
      yield* child;
    }
  }
}

const children = [
  new Comment('good comment', []),
  new Comment('bad comment', []),
  new Comment('meh', [])
];

const tree = new Comment('Great post!', children);

const values = [];
for(let value of tree){
  values.push(value);
}

console.log(values);