mapContaining and setContaining asymmetric matchers

src/core/util.js

@@ -133,5 +133,24 @@ getJasmineRequireObj().util = function(j$) {
     };
   })();
 
+  function StopIteration() {}
+  StopIteration.prototype = Object.create(Error.prototype);
+  StopIteration.prototype.constructor = StopIteration;
+
+  // useful for maps and sets since `forEach` is the only IE11-compatible way to iterate them
+  util.forEachBreakable = function(iterable, iteratee) {
+    function breakLoop() {
+      throw new StopIteration();
+    }
+
+    try {
+      iterable.forEach(function(value, key) {
+        iteratee(breakLoop, value, key, iterable);
+      });
+    } catch (error) {
+      if (!(error instanceof StopIteration)) throw error;
+    }
+  };
+
   return util;
 };