router.start(): add callback after app rendered

Author: yyx990803

src/index.js

@@ -54,6 +54,7 @@ class Router {
 
     // state
     this._started = false
+    this._startCb = null
     this._currentRoute = {}
     this._currentTransition = null
     this._previousTransition = null

src/router/api.js

@@ -109,15 +109,17 @@ export default function (Vue, Router) {
    *
    * @param {VueConstructor} App
    * @param {String|Element} container
+   * @param {Function} [cb]
    */
 
-  Router.prototype.start = function (App, container) {
+  Router.prototype.start = function (App, container, cb) {
     /* istanbul ignore if */
     if (this._started) {
       warn('already started.')
       return
     }
     this._started = true
+    this._startCb = cb
     if (!this.app) {
       /* istanbul ignore if */
       if (!App || !container) {

src/router/internal.js

@@ -170,6 +170,10 @@ export default function (Vue, Router) {
       startTransition()
     }
 
+    if (!this._rendered && this._startCb) {
+      this._startCb.call(null)
+    }
+
     // HACK:
     // set rendered to true after the transition start, so
     // that components that are acitvated synchronously know

test/unit/specs/core.js

@@ -20,7 +20,12 @@ describe('Core', function () {
     var App = Vue.extend({
       template: '<div><router-view></router-view></div>'
     })
-    router.start(App, el)
+    var cb = jasmine.createSpy()
+    router.start(App, el, function () {
+      expect(router.app).toBeTruthy()
+      cb()
+    })
+    expect(cb).toHaveBeenCalled()
     assertRoutes([
       ['/a', 'AAA'],
       ['/b', 'BBB'],