Checking if a key exists in a JavaScript object?

Question

How do I check if a particular key exists in a JavaScript object or array?

If a key doesn't exist, and I try to access it, will it return false? Or throw an error?

Answer 1

For checking if a key exists in a JavaScript object you can use in operator see the following code:-

"key" in obj

To check if a key doesn't exist, parenthesis is must use:

!("key" in obj)