Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

Open brackets must be closed by the same type of brackets.
Open brackets must be closed in the correct order.
Every close bracket has a corresponding open bracket of the same type.

Example 1:

Input: s = "()"
Output: true

var isValid = function(s) {
     const map = {
        '(':')',
        '{':'}',
        '[':']',        
    }
    let stack = []
    for (let c of s) {
        if (c in map){ 
            stack.push(c)
        } else if (map[stack.pop()] !== c) {
            return false
        }
    }
    return !stack.length
};