JavaScript SyntaxError “variable” is a reserved identifier

This JavaScript exception variable is a reserved identifier occurs if the reserved keywords are used as identifiers.

Message:

SyntaxError: The use of a future reserved word for an identifier is invalid (Edge)
SyntaxError: “x” is a reserved identifier (Firefox)
SyntaxError: Unexpected reserved word (Chrome)

Error Type:

SyntaxError

What happened?



When Reserved keywords are used as identifiers they will throw error. enum is reserved in both strict and sloppy mode. while the following keywords are reserved in strict mode.

  • implements
  • package
  • public
  • interface
  • private
  • protected
  • let
  • static

Example 1: The package is an identifier in strict mode, So it will work fine here.

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<script>
    var package = "This is GeeksForGeeks"; 
    document.write(package);
</script>

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Output:

This is GeeksForGeeks

Example 2: The enum is an identifier, So it will throw SyntaxError.

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<script>
    var enum = "This is GeeksForGeeks"; 
    document.write(enum);
</script>

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Output:

SyntaxError: Unexpected reserved word

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