 
The following case-sensitive words may not be used as identifier names:
| abstract | boolean | break | byte | 
| case | catch | char | class | 
| const | continue | debugger | default | 
| delete | do | double | else | 
| enum | export | extends | final | 
| finally | float | for | function | 
| goto | if | implements | import | 
| in | instanceof | int | interface | 
| long | native | new | package | 
| private | protected | public | return | 
| short | static | super | switch | 
| synchronized | this | throw | throws | 
| transient | try | typeof | var | 
| void | volatile | while | with | 
Many of these words are already used in existing JavaScript versions, while the rest are reserved for possible use in future versions.
 
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