Capabilities

A capability is a named feature the host provides. A script can require one:

assertCapability('HTTP')

If the host does not provide it, the program stops with Function error and assertCapability failed: capability HTTP is not present. The desktop interpreter provides FS, random and HTTP. Embedded hosts and ports provide their own set, see Platforms & Ports.

Put assertions at the top of a script so it fails fast on a host that cannot run it.