Problem can also be found here: https://www.hackerrank.com/contests/programming-interview-questions/challenges/balanced-delimiters

balanced_delimiters.js

function isValid(s) {    
	var stack = [];
	var rightChars = [')', '}', ']'];
	
	for (var i = 0; i < s.length; i++) {
		var curr = s[i];
		if (stack.length > 0 && isInArray(curr, rightChars)) {
			var top = stack.pop();
			if (curr === ')' && top !== '(') return false;
			if (curr === ']' && top !== '[') return false;
			if (curr === '}' && top !== '{') return false;
		}
		else {
			if (curr !== ' ')   stack.push(curr);
		}
	}
	return true;
}

function isInArray(value, A) {
	return A.indexOf(value) > -1;
}

How about the input [?