brackets.js

function isBalanced(str) {
    const strArr = str.split('');

    let balanced = true;
    let stack = [];

    const len = strArr.length;
    for (i = 0; i < len; i++) {
        switch (strArr[i]) {
            case '{':
            case '(':
            case '[':
                stack.push(strArr[i]);
                break;
            case '}':
            case ')':
            case ']':
                if (stack[stack.length - 1] === getPair(strArr[i])) {
                    stack.pop();
                } else {
                    balanced = false;
                }
                break;
            default:
                console.log('main panic');
        }
        if (!balanced) {
            break;
        }
    }

    return balanced && stack.length === 0;
}

function getPair(char) {
    switch (char) {
        case '}':
            return '{';
        case ')':
            return '(';
        case ']':
            return '[';
        default:
            console.log('get pair panic');
    }
}


console.log(isBalanced('(((({{{{{[[[]]]}}}}}))))')); // true
console.log(isBalanced('[()[]')); // false
console.log(isBalanced('{}()[]')); // true