JS: Valid String Closures.

validClosures.js

/*
Return TRUE or FALSE whether the string has valid closures.
A valid closure can be: () or ({}) or []({}).
An invalid closure interrupts open/close characters.
Each opener character must have a closer character.
Each closer character must have an opener character.
*/

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

const validPattern = str => {
    let invalid = false
    const arr = str.split('')
    const openers = Object.keys(patterns)
    const closers = Object.values(patterns)
    const o = []
    const c = []

    arr.map((char, i) => {
        if (openers.includes(char)) o.push(char)
        if (closers.includes(char)) c.push(char)

        const prev = arr[i - 1]
        const next = arr[i + 1]
        const openIndex = openers.findIndex(i => i === prev)
        const closeIndex = closers.findIndex(i => i === next)

        if (openers.includes(prev) && closers.includes(next) && openIndex === closeIndex) {
            invalid = true
        }
    })

    if (invalid) return false

    return (o.length !== c.length) ? false : true
}

console.log(validPattern('{([])}'))  // TRUE
console.log(validPattern('{}[]()'))  // TRUE
console.log(validPattern('{()}[]'))  // TRUE
console.log(validPattern('[)]'))     // FALSE
console.log(validPattern('{[]}('))   // FALSE
console.log(validPattern('}{}'))     // FALSE
console.log(validPattern('{[]'))     // FALSE
console.log(validPattern('{[(])]}')) // FALSE
console.log(validPattern('[(])'))    // FALSE