Here is an example (produced with the Node.js REPL):
ClojureScript:cljs.user> (ffirst (js/Date.)) Error: Mon Feb 09 2015 21:33:02 GMT-0500 (EST) is not ISeqable at Object.seq (.../cljs/core.cljs:727:20) at Object.first (.../cljs/core.cljs:736:16) at ffirst (.../cljs/core.cljs:1155:11) ...
ClojureScript:cljs.user> (ffirst (js/Date.)) Error: Mon Feb 09 2015 21:41:14 GMT-0500 (EST) is not ISeqable cljs.core/seq (.../cljs/core.cljs:727:13) cljs.core/first (.../cljs/core.cljs:736:7) cljs.core/ffirst (.../cljs/core.cljs:1155:3) ...
Also in that release is a small related bonus: ClojureScript REPLs now support
*e, the last exception caught (a feature already available in Clojure REPLs):
ClojureScript:cljs.user> *e #<Error: Mon Feb 09 2015 21:33:02 GMT-0500 (EST) is not ISeqable>