# Metadata
Platforms: desktop, server, mobile OS: mac, windows, linux, ios, android Introduced: 1.0 Security:
# Syntax
the functionNames
# Examples
the functionNames
if myHandlerName is in the functionNames then answer "Choose another name."
# Description
Use the functionNames function to check whether a particular function already exists in LiveCode, to avoid using a reserved word for your own custom function handlers.
The functionNames function returns all the built-in functions that can be used in LiveCode, including synonyms.
# Tags
# See
- **keyword:** line - **function:** constantNames, propertyNames, commandNames, variableNames, colorNames - **glossary:** handler, LiveCode, custom function, function, return, reserved word - **control structure:** function