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Using a function directly or by declaring it to a variable

I'm new to software development and trying to understand the basics of JavaScript. In the code below, if I write iterator.next() instead of charAt in "while", the result changes. Can you explain this to me why does it only return 1 when I type iterator.next directly?

  const str = '123';
  const iterator = str[Symbol.iterator]()

  let charAt = iterator.next()

  while (!charAt.done) {
    console.log(charAt.value)
    charAt = iterator.next()
    // output: "1"
    //         "2"
    //         "3"
  }

  const str = '123';
  const iterator = str[Symbol.iterator]()

  let charAt = iterator.next()

  while (!iterator.next().done) {
    console.log(charAt.value)
    charAt = iterator.next()
    // output: "1"
  }

about 4 years ago · Juan Pablo Isaza

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Answer 1 · 2022-06-25T04:09:29.258Z

It's easier to see if you have a longer string.

  const str = '12345678';
  const iterator = str[Symbol.iterator]()

  let charAt = iterator.next()

  while (!iterator.next().done) {
    console.log(charAt.value)
    charAt = iterator.next()
    // output: "1"
  }

Because you call next() in two different places inside the loop (as well as once outside the loop), every time you go around the loop, you advance two places.

Answer 2 · 2022-06-25T04:09:29.267Z

u have used iterator.next() three times,
for the fitst time it returs 1, which u assign to charAt,
then in while loop condition iterator.next() returns 2, but u have not assigned it any where,
and because u have not updated your charAt value yet, it logs 1,
then iterator.next() returns 3, which u assign to charAt,
but in second pass of while loop iterator.next() returns {done:true}, and the control doesn't goes inside loop

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Using a function directly or by declaring it to a variable

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Andres GPT