Valid Parentheses

/**
 * @param {string} s
 * @return {boolean}
 */
var isValid = function(s) {
    var stack = [];

    for (var i = 0; i < s.length; i++) {
        if (stack.length < 1) {
            stack.push(s[i]);
        } else if ((s[i] === ')' && stack[stack.length - 1] === '(') || (s[i] === ']' && stack[stack.length - 1] === '[') || (s[i] === '}' && stack[stack.length - 1] === '{')) {
            stack.pop();
        } else {
            stack.push(s[i]);
        }
    }

    return stack.length < 1;
};