Add withExtraArgument()

src/index.js

@@ -1,9 +1,14 @@
-export default function thunkMiddleware({ dispatch, getState }) {
-  return next => action => {
+function createThunkMiddleware(extraArgument) {
+  return ({ dispatch, getState }) => next => action => {
     if (typeof action === 'function') {
-      return action(dispatch, getState);
+      return action(dispatch, getState, extraArgument);
     }
 
     return next(action);
   };
 }
+
+const thunk = createThunkMiddleware();
+thunk.withExtraArgument = createThunkMiddleware;
+
+export default thunk;

test/index.js

@@ -76,4 +76,19 @@ describe('thunk middleware', () => {
       }
     });
   });
+
+  describe('withExtraArgument', () => {
+    it('must pass the third argument', done => {
+      const extraArg = { lol: true };
+      thunkMiddleware.withExtraArgument(extraArg)({
+        dispatch: doDispatch,
+        getState: doGetState,
+      })()((dispatch, getState, arg) => {
+        chai.assert.strictEqual(dispatch, doDispatch);
+        chai.assert.strictEqual(getState, doGetState);
+        chai.assert.strictEqual(arg, extraArg);
+        done();
+      });
+    });
+  });
 });