Predicates

Predicates are functions that return a boolean value based on the context of a Feathers service call. They can be used to conditionally execute hooks or logic based on the state of the request, such as whether the user is authenticated, if the data is an array, or any other custom condition you define.

Built-in Predicates

Predicate	Description
every	Returns a predicate that is true only when all given predicates are true (logical AND). Supports both sync and async predicates. Short-circuits on the first false result. Undefined predicates in the list are skipped.
isContext	Returns a predicate that checks whether the hook context matches the given criteria. You can filter by path (service name), type (before/after/around/error), and/or method (find/get/create/update/patch/remove).
isMulti	Checks if the current hook context represents a multi operation. Returns true for find, for create with array data, and for patch/remove with id === null. Returns false for get and update.
isPaginated	Checks if the current find operation is paginated by inspecting params.paginate and the service's pagination options via getPaginate. Returns false for all methods other than find or when pagination is disabled.
isProvider	Returns a predicate that checks the transport provider of the service call. Matches against 'rest', 'socketio', 'external' (any external provider), or 'server' (internal call without a provider).
not	Negates a sync or async predicate function, inverting its boolean result. Useful for composing conditions like "not external" or "not multi".
shouldSkip	Returns a predicate that checks params.skipHooks to determine if a hook should be skipped. Matches by hook name, hook type (e.g. 'before'), prefixed name (e.g. 'before:myHook'), or 'all' to skip everything. Designed to be used with skippable and addSkip.
some	Returns a predicate that is true when any of the given predicates is true (logical OR). Supports both sync and async predicates. Short-circuits on the first true result. Undefined predicates in the list are skipped.

Hooks that are meant to be used with predicates

Hook	Description
iff	Conditionally executes a series of hooks when the predicate is truthy. The predicate can be a boolean value or a sync/async function. Supports an .else(...) chain for the falsy branch. Also exported as when.
iffElse	Executes one array of hooks when the predicate is truthy, or another array when it is falsy. The predicate can be a boolean or a sync/async function. Unlike iff, both branches are provided upfront without chaining.
skippable	Wraps a hook so it can be conditionally skipped based on a predicate. When the predicate returns true, the wrapped hook is skipped entirely. Commonly used with shouldSkip and addSkip for runtime hook control.
throwIf	Throws a BadRequest error when the given predicate function returns true. The predicate receives the hook context and can be async. Useful for validating conditions before proceeding with a request.
unless	Executes a series of hooks when the predicate is falsy --- the inverse of iff. The predicate can be a boolean or a sync/async function. Useful for applying hooks to all contexts except those matching a condition.

Custom Predicates

You can easily create custom predicates like:

const isSingleData = (context) => !Array.isArray(context.data);

or

const isAuthenticated = (context) => !!context.params?.authenticated;