<a href="#/html" rel="external nofollow" rel="external nofollow" >html课程</a> 
<a href="#/css" rel="external nofollow" rel="external nofollow" >css课程</a> 

window.onload = function(){
      //当hash发生变化的时候， 会产生一个事件 onhashchange
      window.onhashchange = function(){
        console.log( '你的hash改变了' );
        //location对象是 javascript内置的(自带的)
        console.log( location );
      }
    }

 <input type="button" value="33选5">
 <div></div>

window.onload = function(){
      var oBtn = document.querySelector("input");
      var oDiv = document.querySelector("div");
      //33->max 5->num
      function buildNum( max, num ){
        var arr = [];
        for( var i = 0; i < max; i++ ){
          arr.push( i + 1 );
        }
        var target = []; //从1-33这33个数字中 随机选出5个数
        for( var i = 0; i < num; i++ ){
          target.push( arr.splice( Math.floor( Math.random() * arr.length ), 1 ) );
        }
        return target;
      }
      oBtn.onclick = function(){
        var num = buildNum( 33, 5 );
        oDiv.innerHTML = num;
        location.hash = num;
      }
      window.onhashchange = function(){
        oDiv.innerHTML = location.hash.substring(1);
      }
    }

header,
    footer {
      height: 100px;
      background: #ccc;
    }

    section {
      width: 60%;
      height: 400px;
      background: #eee;
      float: left;
    }

    sidebar {
      width: 40%;
      height: 400px;
      background: #999;
      float: left;
    }

    .clear {
      clear: both;
    }

<header>
    头部
  </header>
  <section>
    <ul>
      <li><a href="#/" rel="external nofollow" >全部</a></li>
      <li><a href="#/html" rel="external nofollow" rel="external nofollow" >html课程</a></li>
      <li><a href="#/css" rel="external nofollow" rel="external nofollow" >css课程</a></li>
      <li><a href="#/javascript" rel="external nofollow" >javascript课程</a></li>
    </ul>
  </section>
  <sidebar>
    右边
  </sidebar>
  <div class="clear"></div>
  <footer>
    底部
  </footer>

(function(){
      var Router = function(){
        /*
          this.routes['/'] = function(){}  
          this.routes['/html'] = function(){}
        */ 
        this.routes = {};//用来保存路由
        this.curUrl = ''; //获取当前的hash
      }
      Router.prototype.init = function(){ //监听路由变化
        //call,apply
        window.addEventListener( 'hashchange', this.reloadPage.bind(this) );
      }
      Router.prototype.reloadPage = function(){
        this.curUrl = location.hash.substring(1) || '/';
        this.routes[this.curUrl]();    
      }
      Router.prototype.map = function( key, callback ){ //保存路由对应的函数
        this.routes[key] = callback;
        // console.log( this.routes );
      } 
      window.Router = Router;
    })();

    var oRouter = new Router();
    oRouter.init();
    oRouter.map( '/', function(){
      var oSidebar = document.querySelector("sidebar");
      oSidebar.innerHTML = 'ghostwu提供html,css,javascript从0基础到精通系列课程，只要会开关机，就能学会';
    });
    oRouter.map('/html', function(){
      var oSidebar = document.querySelector("sidebar");
      oSidebar.innerHTML = 'ghostwu提供html5从入门到精通的课程';
    });
    oRouter.map('/css', function(){
      var oSidebar = document.querySelector("sidebar");
      oSidebar.innerHTML = 'ghostwu提供从入门到玩转css3课程';
    });
    oRouter.map('/javascript', function(){
      var oSidebar = document.querySelector("sidebar");
      oSidebar.innerHTML = "ghostwu提供从0基础到精通javascript系列课程";
    });