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JScript Identifiers

In JScript, identifiers are used to:

  • name variables, constants, functions, classes, interfaces, and enumerations

  • provide labels for loops (not used very often).

JScript is a case-sensitive language. Consequently, a variable named myCounter is different from a variable named MyCounter. Variable names can be of any length. The rules for creating valid variable names are as follows:

  • The first character must be a Unicode letter (either uppercase or lowercase) or an underscore (_) character. Note that a number cannot be used as the first character.

  • Subsequent characters must be letters, numbers, or underscores.

  • The variable name must not be a reserved word.

Here are some examples of valid identifiers:


Here are some examples of invalid identifiers:

99Balloons // Cannot begin with a number. 
Smith&Wesson // The ampersand (&) character is not a valid character for variable names. 

When choosing identifiers, avoid JScript reserved words and words that are already the names of intrinsic JScript objects or functions, such as String or parseInt.