how to to if any key vailue paisr exist in an object code example

Example 1: how to check if a key exists in an object javascript

!("key" in obj) // true if "key" doesn't exist in object
!"key" in obj   // ERROR!  Equivalent to "false in obj"

Example 2: check if a key exists in an object javascript

"key" in obj // true, regardless of the actual value