string[index] doesn't work correctly

[ngocdaothanh]

See the line console.log(string, i, char) below in the program to check if parentheses are balanced:

function check(string) {
  let count = 0

  for (let i = 0; i < string.length; i++) {
    const char = string[i]
    console.log(string, i, char)

    if (char === '(')
      count++
    else if (char === ')')
      count--

    console.log(count)
    if (count < 0) return false
  }

  return count === 0
}

console.log(check('()(()())'))

Expected output:

()(()()) 0 (
()(()()) 1 )
()(()()) 2 (
...

Actual output:

()(()()) 0 (
()(()()) 1 (
()(()()) 2 (
...

It seems that in this program string[index] always returns the first character.

[basicer]

The problem here is that ES6 block scoping isn't implemented yet, so the const applies to the whole function, and the assignment silently fails. Fixing #15 will make this more obvious.

[ngocdaothanh]

I think there's bug somewhere, because when the program is in ES5, it doesn't work as expected:

function check(string) {
  var count = 0

  for (var i = 0; i < string.length; i++) {
    var char = string[i]
    console.log(string, i, char)

    if (char === '(')
      count++
    else if (char === ')')
      count--

    if (count < 0) return false
  }

  return count === 0
}

console.log(check('()(()())'))

[basicer]

What is the expected output? I get:

Rambi:esper.js basicer$ node j.js 
()(()()) 0 (
()(()()) 1 )
()(()()) 2 (
()(()()) 3 (
()(()()) 4 )
()(()()) 5 (
()(()()) 6 )
()(()()) 7 )
true

[ngocdaothanh]

I've just try running with the demo site again:
https://esper.js.org

The output looks good now. So it was because of the const problem as you explained.