All standard JavaScript methods are available, and a Rudder-specific library, prefixed with rudder. also provides some extra utilities. This library is documented below.

For example, to get the first 3 letters of each node’s hostname, you can write:

[Tip]Limitation of the scripting language

JavaScript expressions are evaluated in a sandboxed JavaScript environment. It has some limitations, such as:

  • It cannot write on the filesystem
  • Scripts are killed after 5 seconds of execution, to prevent overloading the system