what is the difference between these two codes. One return error and second one return no error?

Question

When I use var in the loop I get no error.

function reverseString(str) {
  for (var reversedStr = "", i = str.length - 1; i >= 0; i--) {
    reversedStr += str[i];
  }
  return reversedStr;
}
console.log(reverseString("hello"))
//OUTPUT --------> olleh

when I use let in the loop I get an error.

function reverseString(str) {
  for (let reversedStr = "", i = str.length - 1; i >= 0; i--) {
    reversedStr += str[i];
  }
  return reversedStr;
}
console.log(reverseString("hello"))
//OUTPUT -------->Uncaught ReferenceError: reversedStr is not defined

Does this answer your question? [What's the difference between using "let" and "var"?](https://stackoverflow.com/questions/762011/whats-the-difference-between-using-let-and-var) — Mady Daby, Apr 20 '21 at 11:44

score 0 · Accepted Answer · answered Apr 20 '21 at 11:45

0

Scoping.

In your first example, var reversedString is function-scoped, and accessible in the whole function.

In your second example, let reversedString is block-scoped, and only accessible in the for loop.

answered Apr 20 '21 at 11:45

Cerbrus

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2

And that is an easily found dupe. – mplungjan Apr 20 '21 at 11:45
1

If the answer is more complicated or different to the documentation, then I will also answer a dupe. This however not. – mplungjan Apr 20 '21 at 11:50
1

I wasn't talking about you, tho. – Cerbrus Apr 20 '21 at 11:51
1

I figured that out after doing the math ;) – mplungjan Apr 20 '21 at 11:51

what is the difference between these two codes. One return error and second one return no error?

1 Answers1