public
as a visibility modifier technically does nothing (all class members are public by default); it exists as an explicit counterpart to private
. It's legal only inside classes.
export
does two different things depending on its context (on a top-level member in a file or in a module
block).
At the top level of a file, export
means that the containing file is an external module (i.e. it will be loaded using RequireJS, Node's require
command, or some other CommonJS/AMD-compliant loader) and that the symbol you put export
on should be an exported member of that external module.
Inside a module
block, export
means that the specified member is visible outside that module block. The default for things in module
blocks is "closure privacy" -- unexported objects are not visible outside the module. When a declaration inside a module
has the export
modifier, it instead becomes a property of the module object that can be accessed from outside the module.
There is no place in the language where both public
and export
are legal, so choosing is relatively easy in that regard.