behnamazimi

const data = ["A", "B", "C"];
for (let item of data) {
 console.log(item)
} //o: A B C

behnamazimi

const data = {
 items: ["A", "B", "C"],
 pointerIndex: 0,
 next() {
   if (this.pointerIndex < this.items.length) // if not done
     return { value: this.items[this.pointerIndex++], done: false }
   else // if done
     return { value: undefined, done: true };
 }
}

behnamazimi

let dataElement = data.next();

while (!dataElement.done) {
  console.log(dataElement.value)
  dataElement = data.next();
} //o: A B C

behnamazimi

console.log(data.next()) //o: {value: "A", done: false}
console.log(data.next()) //o: {value: "B", done: false}
console.log(data.next()) //o: {value: "C", done: false}
console.log(data.next()) //o: {value: undefined, done: true}

behnamazimi

const data = {
 items: ["A", "B", "C"],
 pointerIndex: 0,
 next() {
   if (this.pointerIndex < this.items.length) // if done
     return { value: this.items[this.pointerIndex++], done: false }
   else // if not done
     return { value: undefined, done: true };
 }
}

behnamazimi

const symblOne = Symbol("Description");
const symblTwo = Symbol("Description");

symblOne === symblTwo //o: false

behnamazimi

const symblOne = Symbol();

const myObject = {
  [symblOne]: "My Data",
  //...
}

console.log(myObject[symblOne]) //o: "My Data"

behnamazimi

const myObject = {
  [Symbol()]: "My Data",
  //...
}

console.log(myObject) //o: {Symbol(): "My Data"}

behnamazimi

const myObject = {
  [Symbol("myKey")]: "My Data",
  //...
}

console.log(Object.getOwnPropertySymbols(myObject)); //o: [Symbol(myKey)]

const symbl = Object.getOwnPropertySymbols(myObject)[0]
console.log(myObject[symbl]) //o: "My Data"

behnamazimi

const data = {
 items: ["A", "B", "C"],
 pointerIndex: 0,
 [Symbol.iterator]: function () {
   if (this.pointerIndex < this.items.length) // if done
     return { value: this.items[this.pointerIndex++], done: false }
   else // if not done
     return { value: undefined, done: true };
 }
}