Appendix C. Reserved Words

The following words can’t be used as an identifier (the name of a variable, constant, property, or function) in JavaScript:

  • await (reserved for future use)

  • break

  • case

  • class

  • catch

  • const

  • continue

  • debugger

  • default

  • delete

  • do

  • else

  • enum (reserved for future use)

  • export

  • extends

  • false (literal value)

  • finally

  • for

  • function

  • if

  • implements (reserved for future use)

  • import

  • in

  • instanceof

  • interface (reserved for future use)

  • let

  • new

  • null (literal value)

  • package (reserved for future use)

  • private (reserved for future use)

  • protectd (reserved for future use)

  • public (reserved for future use)

  • return

  • super

  • static (reserved for future use)

  • switch

  • this

  • throw

  • true (literal value)

  • try

  • typeof

  • var

  • void

  • while

  • with

  • yield

The following words were reserved in ECMAScript specifications 1–3. They are no longer reserved words, but I discourage their use, as JavaScript implementations may (incorrectly) consider them reserved words:

  • abstract

  • boolean

  • byte

  • char

  • double

  • final

  • float

  • goto

  • int

  • long

  • native

  • short

  • synchronized

  • transient

  • volatile

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