* add info helper

* add filter-externs helper
* eval comments
  - the problem is complex type expressions

src/main/clojure/cljs/externs.clj

@@ -313,6 +313,24 @@
                 (parse-externs (resource->source-file rsrc))
                 (:module desc))}))))
 
+(defn info
+  "Helper for grabbing var info from an externs map.
+  Example:
+    (info externs '[Number isNaN])
+  See `externs-map`"
+  [externs props]
+  (-> externs
+    (get-in (butlast props))
+    (find (last props))
+    first meta))
+
+(defn filtered-externs [f]
+  (->>
+    (filter
+      #(= f (.getName %))
+      (default-externs))
+    first parse-externs index-externs))
+
 (comment
   (require '[clojure.java.io :as io]
            '[cljs.closure :as closure]

src/test/clojure/cljs/externs_infer_tests.clj

@@ -486,6 +486,21 @@
                  :with-core? true})]
       (is (empty? @ws)))))
 
+(comment
+
+  (externs/info
+    (::ana/externs @(env/default-compiler-env))
+    '[console])
+
+  (externs/info
+    (::ana/externs @(env/default-compiler-env))
+    '[crypto])
+
+  (-> (externs/filtered-externs "externs.zip//w3c_webcrypto.js")
+    (externs/info '[crypto]))
+
+  )
+
 (comment
   (binding [ana/*cljs-ns* ana/*cljs-ns*]
     (ana/no-warn