Add Matching Multiple Values In A Switch Statement as a javascript til

README.md

@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
 [til.hashrocket.com](https://til.hashrocket.com/).
 
-_564 TILs and counting..._
+_565 TILs and counting..._
 
 ---
 
@@ -215,6 +215,7 @@ _564 TILs and counting..._
 - [Globally Install A Package With Yarn](javascript/globally-install-a-package-with-yarn.md)
 - [Immutable Remove With The Spread Operator](javascript/immutable-remove-with-the-spread-operator.md)
 - [Initialize A New JavaScript Project With Yarn](javascript/initialize-a-new-javascript-project-with-yarn.md)
+- [Matching Multiple Values In A Switch Statement](javascript/matching-multiple-values-in-a-switch-statement.md)
 - [Numbers Are Empty](javascript/numbers-are-empty.md)
 - [Object Initialization With Shorthand Property Names](javascript/object-initialization-with-shorthand-property-names.md)
 - [Random Cannot Be Seeded](javascript/random-cannot-be-seeded.md)

javascript/matching-multiple-values-in-a-switch-statement.md

@@ -0,0 +1,28 @@
+# Matching Multiple Values In A Switch Statement
+
+Switch statements are a handy way to execute different branches of code
+based on a value match. This is often what is used in Redux reducers when
+updating the state in response to certain actions.
+
+But what if you need multiple values to result in the same branch of
+execution without duplicating the code?
+
+The execution of a switch statement falls through, so after one match, it
+will continue to try and do subsequent matches if you don't interrupt the
+execution with a `break` or `return`. Conveniently, this solves our problem
+of matching multiple values.
+
+```javascript
+switch (action.type) {
+  case "UPDATE_NAME":
+  case "UPDATE_DURATION":
+    let newData = anotherReducer(state.data, action);
+    return { ...state, data: newData };
+  default:
+    return state;
+}
+```
+
+See the [MDN
+docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/switch)
+for more details.