protocolsince v0.0-927Edit
implemented for ArrayNodeSeq Atom BlackNode ChunkedCons ChunkedSeq Cons EmptyList IndexedSeq IntegerRange KeySeq Keyword LazySeq List MapEntry Namespace NeverEquiv NodeSeq ObjMap PersistentArrayMap PersistentArrayMapSeq PersistentHashMap PersistentHashSet PersistentQueue PersistentQueueSeq PersistentTreeMap PersistentTreeMapSeq PersistentTreeSet PersistentVector RSeq Range RedNode Repeat Subvec Symbol TaggedLiteral UUID ValSeq Var default js/Date number

Source docstring:
Protocol for adding value comparison functionality to a type.
Source code @ clojurescript:src/main/cljs/cljs/core.cljs
(defprotocol IEquiv
  (^boolean -equiv [o other]
    "Returns true if o and other are equal, false otherwise."))