前端路由原理及vue-router介绍

**
 * 添加 url hash 变化的监听器
 */
setupListeners () {
  const router = this.router

  /**
   * 每当 hash 变化时就解析路径
   * 匹配路由
   */
  window.addEventListener(‘hashchange‘, () => {
    const current = this.current
    /**
     * transitionTo: 
     * 匹配路由
     * 并通过路由配置，把新的页面 render 到 ui-view 的节点
     */this.transitionTo(getHash(), route => {
      replaceHash(route.fullPath)
    })
  })
}

            export class HTML5History extends History {
  constructor (router, base) {
    super(router, base)
    
            /*
            *
     * 原理还是跟 hash 实现一样
     * 通过监听 popstate 事件
     * 匹配路由，然后更新页面 DOM
     
            */
            
    window.addEventListener(‘popstate‘, e => {
      const current = this.current

      // Avoiding first `popstate` event dispatched in some browsers but first// history route not updated since async guard at the same time.
      const location = getLocation(this.base)
      if (this.current === START && location === initLocation) {
        return
      }

      this.transitionTo(location, route => {
        if (supportsScroll) {
          handleScroll(router, route, current, true)
        }
      })
    })
  }

  go (n) {
    window.history.go(n)
  }

  push (location, onComplete, onAbort) {
    const { current: fromRoute } = thisthis.transitionTo(location, route => {
      // 使用 pushState 更新 url，不会导致浏览器发送请求，从而不会刷新页面
      pushState(cleanPath(this.base + route.fullPath))
      onComplete && onComplete(route)
    }, onAbort)
  }

  replace (location, onComplete, onAbort) {
    const { current: fromRoute } = thisthis.transitionTo(location, route => {
      // replaceState 跟 pushState 的区别在于，不会记录到历史栈
      replaceState(cleanPath(this.base + route.fullPath))
      onComplete && onComplete(route)
    }, onAbort)
  }
}