Binary Search Tree Validation in JavaScript

Binary Search Tree Validation.js

//Solution 1

const isValidBST = function(root, min = Number.MIN_SAFE_INTEGER, max = Number.MAX_SAFE_INTEGER) {
    if(root == null) return true
    if(root.val >= max || root.val <= min) return false
    return isValidBST(root.left, min, root.val) && isValidBST(root.right, root.val, max)
};



//Solution 2

const isValidBST = root => {
 if (!root) return true; 
 
 const stack = [];
 let prevNode = null;
 
 while(root != null || stack.length > 0) {
   while(root != null) {
     stack.push(root);
     root = root.left;
   }

   root = stack.pop();
   if (prevNode && prevNode.val >= root.val) return false;
   prevNode = root;
   root = root.right;
 }
 
 return true;
};