Undefined occurs for example when you don’t pass a parameter, or when a function doesn’t return a value (but you read/store it anyway). Null comes for example f

Undefined occurs for example when you don’t pass a parameter, or when a function doesn’t return a value (but you read/store it anyway). Null comes for example from JSON, from nullable SQL columns, and it is passed explicitly to say „this value is empty“ very commonly in libraries.