Question

• Create a method on the Iterator class called forEach, which appropriate behavior.
• This method should use next(), and should not use this._array.forEach!
• Take note of what should happen if you call forEach twice on the same Iterator instance.
• The estimated output is commented below
• In javascript please

class Iterator {
  constructor(arr){
    this[Symbol.iterator] = () => this
    this._array = arr
    this.index = 0
  }

  next(){
    const done = this.index >= this._array.length
    const value = this._array[this.index++]
    return {done, value}
  }

  //YOUR WORK HERE
}


const arr = ["a","b","c","d","e"]
const it = new Iterator(arr)
it.forEach(item => console.log(item))

console.log("Let's try that again...")

it.forEach(item => console.log(item)) 
//produces no output

console.log("Extra credit: with indices...")

const it2 = new Iterator(arr)
it2.forEach((item, index) => console.log(item, index))


/*
a
b
c
d
e
Let's try that again...
Extra credit: with indices...
a 0
b 1
c 2
d 3
e 4
*/

Answer 1

Code in Javascript

class Iterator {
  constructor(arr){
    this[Symbol.iterator] = () => this
    this._array = arr
    this.index = 0
  }

  next(){
    const done = this.index >= this._array.length
    const value = this._array[this.index++]
    return {done, value}
  }

  forEach(func){
      while(this.index<this._array.length){
          const index = this.index;
          const item = this._array[index];
          func.call(this,item, index);
          this.index++;
      }
  }
}


const arr = ["a","b","c","d","e"]
const it = new Iterator(arr)
it.forEach(item => console.log(item))

console.log("Let's try that again...")

it.forEach(item => console.log(item)) 
// produces no output

console.log("Extra credit: with indices...")

const it2 = new Iterator(arr)
it2.forEach((item, index) => console.log(item, index))

Sample Output

Explanation

We are passing a function inside the forEach function and for every value from current index to the end we are calling this passed function. Let me know in the comments if you have any confusion.