optional-require
NodeJS Require that let you handle module not found error without try/catch
optional
Allows you to optionally include modules without surrounding everything with 'try/catch'
browserify-optional
A browserify transform that allows optional dependencies in try..catch blocks
optional-js
Optionals for JS - wrapper for possibly undefined values, inspired by Java Optional API
require_optional
Allows you declare optionalPeerDependencies that can be satisfied by the top level module but ignored if they are not.