This is my first time doing a leetcode and I got a binary tree problem (also my first seeing it) although the question seems easy enough I'm having a hard time understanding this specifically
* function TreeNode(val, left, right) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
what does the ? 0 : val) mean after the undefined?
screenshot of leetcode question
leet link: https://leetcode.com/problems/root-equals-sum-of-children/