From Overview of Advanced JavaScript -- Web Scripting Language CPS616 Technologies of the Information Age -- Spring Semester 98. byTom Scavo,Geoffrey C. Fox
When browsing the Web, two pieces of information are considered public: the IP address of the client and the type of browser. All other data are considered private. In particular,
JavaScript does not permit access to the client file system
JavaScript can not establish a direct connection to an arbitrary Internet host