gistfile1.js

function check(brackets_str) {
	'use strict'
	var stack = [],
		brackets_arr = brackets_str.split(''),
		open_brackets = ['(', '[', '{'],
		close_brackets = [')', ']', '}'];

	for (var i = 0, l = brackets_arr.length; i < l; i++) {
		var b = brackets_arr[i];
		if (!!~open_brackets.indexOf(b)) {
			stack.push(b);
		} else if (!!~close_brackets.indexOf(b)) {
			if (stack.length === 0) {
				return false;
			}
			var top = stack.pop();
			if (top == b) {return false;
			}
		}
	}
	if (stack.length === 0) {
		return true;
	}

	return false;
}

function check2(brackets_str) {
	'use strict'
	if (brackets_str === "") {
		return true;
	}
	var stack = [],
		brackets_arr = brackets_str.split(''),
		open_brackets = {'(':"", '[':"", '{':""},
		close_brackets = {')':"", ']':"", '}':""};

	for (var i = 0, l = brackets_arr.length; i < l; i++) {
		var b = brackets_arr[i];
		if (open_brackets[b]) {
			stack.push(b);
		} else if (open_brackets[b]) {
			if (stack.length === 0) {
				return false;
			}
			var top = stack.pop();
			if (top == b) {return false;
			}
		}
	}
	if (stack.length === 0) {
		return true;
	}

	return false;
}