expression reducer and stubbed out component

src/reducers/expression.js

@@ -0,0 +1,29 @@
+const Expression = (state = {
+  data: null,
+  loading: null,
+  error: null,
+}, action) => {
+  switch (action.type) {
+  case "get expression started":
+    return Object.assign({}, state, {
+      loading: true,
+      error: null
+    });
+  case "get expression success":
+    return Object.assign({}, state, {
+      error: null,
+      loading: false,
+      data: action.data.data,
+    });
+  case "get expression error":
+    return Object.assign({}, state, {
+      data: null,
+      loading: false,
+      error: action.data
+    });
+  default:
+    return state;
+  }
+};
+
+export default Expression;