vue-router在ie9及以下history模式支持

参考：

　　https://www.npmjs.com/package/vue-route

　　https://github.com/devote/HTML5-History-API

提要：

　　ie9及以下不支持html5 history新特性

解决：

• npm install html5-history-api
• <!--[if lte IE 9]><script src=“path_to_history.js"></script><![endif]-->
  • issus

    • history.js - IE8+ and other browsers

      history.ielte7.js - IE6+ and other browsers　　　　　　　　　　

    • 使用webpack时 

        1 var supportsPushState = inBrowser && (function () {
        2   var ua = window.navigator.userAgent;
        3
        4   if (
        5     (ua.indexOf('Android 2.') !== -1 || ua.indexOf('Android 4.0') !== -1) &&
        6     ua.indexOf('Mobile Safari') !== -1 &&
        7     ua.indexOf('Chrome') === -1 &&
        8     ua.indexOf('Windows Phone') === -1
        9   ) {
       10     return false
       11   }
       12
       13   return window.history && 'pushState' in window.history
       14 })();

      这里supportsPushState在加载时已经被定义,就算在之后的  require('html5-history-api') 也是没有意义的,缓存虽然是王道可有时用不好真的是个坑。。。。

       var VueRouter = function VueRouter (options) {
         if ( options === void 0 ) options = {};
      
         this.app = null;
         this.apps = [];
         this.options = options;
         this.beforeHooks = [];
         this.resolveHooks = [];
         this.afterHooks = [];
         this.matcher = createMatcher(options.routes || [], this);
      
         var mode = options.mode || 'hash';
         this.fallback = mode === 'history' && !supportsPushState && options.fallback !== false; //这里直接使用了定义好的supportsPushState
      
         if (this.fallback) { //最终还是使用了hash模式
           mode = 'hash';
         }
         if (!inBrowser) {
           mode = 'abstract';
         }
         this.mode = mode;
         switch (mode) {
           case 'history':
             this.history = new HTML5History(this, options.base);
             break
           case 'hash':
             this.history = new HashHistory(this, options.base, this.fallback);
             break
           case 'abstract':
             this.history = new AbstractHistory(this, options.base);
             break
           default:
             {
               assert(false, ("invalid mode: " + mode));
             }
         }
       };　　

#在设计缓存时一定要考虑到上下文的依赖,过时的缓存有啥用呢

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