TapDigit is a simple JavaScript implementation of a math expression lexer, parser, and evaluator.
TapDigit.Lexer splits a math expression into a sequence of tokens. This is useful for e.g. an expression editor with color syntax highlighting.
TapDigit.Parser parses an expression and produces the JSON-formatted syntax tree representation thereof.
TapDigit.Evaluator computes the result of an expression. Variables, constants, and functions supported in the expression syntax can be extended via TapDigit.Context object.
There is also a simple web page (open eval.htm) which demonstrates how it works:
TapDigit is created by @AriyaHidayat. It is distributed under the BSD license.