brackets problem recursive solution with string size reduction

gistfile1.txt

const tests = [
    '()[]{}',
    '(((]))',
    '((()))',
    '](',
    '(()',
    '())'
]

const solutions = [
    true,
    false,
    true,
    false,
    false,
    false
]

const isOpening = c => {
    return ['(', '{', '['].indexOf(c) > -1
}

const isClosing = c => {
    return [')', '}', ']'].indexOf(c) > -1
}

const closers = {
    '(': ')',
    '{': '}', 
    '[': ']'
}

const isValid = str => {
    if (str.split("").some(c => !isOpening(c) && !isClosing(c))) {
        throw new Error("Chars expected to be from '(', '[', '{', ')', ']', '}'")
    }
    if (str.length === 0) {
        return true
    }
    if (!isOpening(str[0])) {
        return false
    }
    let innermostOpenerIndex = 0
    while (isOpening(str[innermostOpenerIndex + 1]) ) {
        innermostOpenerIndex++
    }
    const innermostOpener = str[innermostOpenerIndex]
    const innermostCloser = str[innermostOpenerIndex + 1]
    if(closers[innermostOpener] !== innermostCloser) {
        return false
    }
    const stringWithParensRemoved = str.slice(0, innermostOpenerIndex) + str.slice(innermostOpenerIndex + 2)
    return isValid(stringWithParensRemoved)
}

tests.forEach((test, i) => {
    if(isValid(test) !== solutions[i]) {
        throw new Error(`${test} should be ${solutions[i]}`)
    }
})