So there are some keywords present in javascript language that you can't define as variables, functions, etc anywhere. They are reserved, meaning that they are part of the programming language and can't be reused according to our creative needs.
Here are some of the reserved keywords that are present in javascript:
| Await | Continue | Enum | Instance Of | With |
| Do | Else | For | Package | Yield |
| Const | Finally | In | Super | |
| Break | Import | Null | Try | |
| Case | New | Return | While | |
| Catch | Public | Throw | If | |
| Class | This | Void | Interface | |
| False | Var | Export | Private | |
| Implements | Debugger | Extends | Switch | |
| Let | Default | Function | True |
So these are some of the keywords that are used and each keyword has a specific purpose in Javascript Language just like any other keyword in other languages.