From 6cacc2e17a4b3d9e938c3c36f665c533fcf97f37 Mon Sep 17 00:00:00 2001
From: Arunoda Susiripala <arunoda.susiripala@gmail.com>
Date: Mon, 6 Mar 2017 18:24:59 +0530
Subject: [PATCH] Add beforeHistoryChange router event.

---
 lib/router/index.js  | 2 +-
 lib/router/router.js | 1 +
 readme.md            | 1 +
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/router/index.js b/lib/router/index.js
index 550ef110d3e2..476d0f15d401 100644
--- a/lib/router/index.js
+++ b/lib/router/index.js
@@ -15,7 +15,7 @@ const SingletonRouter = {
 // Create public properties and methods of the router in the SingletonRouter
 const propertyFields = ['components', 'pathname', 'route', 'query']
 const coreMethodFields = ['push', 'replace', 'reload', 'back', 'prefetch']
-const routerEvents = ['routeChangeStart', 'routeChangeComplete', 'routeChangeError']
+const routerEvents = ['routeChangeStart', 'beforeHistoryChange', 'routeChangeComplete', 'routeChangeError']
 
 propertyFields.forEach((field) => {
   // Here we need to use Object.defineProperty because, we need to return
diff --git a/lib/router/router.js b/lib/router/router.js
index 518d1faff774..20829092a4c6 100644
--- a/lib/router/router.js
+++ b/lib/router/router.js
@@ -157,6 +157,7 @@ export default class Router extends EventEmitter {
       return false
     }
 
+    this.emit('beforeHistoryChange', as)
     this.changeState(method, url, as)
     const hash = window.location.hash.substring(1)
 
diff --git a/readme.md b/readme.md
index 4d4037bc43b6..ff05ed3babab 100644
--- a/readme.md
+++ b/readme.md
@@ -310,6 +310,7 @@ Here's a list of supported events:
 - `routeChangeStart(url)` - Fires when a route starts to change
 - `routeChangeComplete(url)` - Fires when a route changed completely
 - `routeChangeError(err, url)` - Fires when there's an error when changing routes
+- `beforeHistoryChange(url)` - Fires just before changing the browser's history
 - `appUpdated(nextRoute)` - Fires when switching pages and there's a new version of the app
 
 > Here `url` is the URL shown in the browser. If you call `Router.push(url, as)` (or similar), then the value of `url` will be `as`.