null if:
- This node is not an OBJECT
- The key does not exist
Safe read-only lookup by key without auto-creation.
Unlike opIndex(string), this method does NOT convert NULL to OBJECT and does NOT create a new member if the key is missing. This makes it safe for read-only access patterns where you don't want to accidentally mutate the node.
This is the preferred method for checking if a key exists before accessing it, and for read-only traversals.
key | The member key to look up. Returns null for empty keys if this node is not an OBJECT (m-70 safe behavior). |
null if:
opIndex for auto-vivifying access (creates missing keys).