var hasPathSum = function(root, targetSum) {

    let sum = 0;

    const helper = (root) => {
        if (root === null) {
            return;
        }

        sum += root.val;

        if (sum === targetSum && (root.left == null && root.right === null)) {
            return true;
        }

        if (helper(root.left)){
            return true;
        }
        if (helper(root.right)) {
            return true;
        };
        sum -= root.val;
    }

    return helper(root) ? true : false;
};