hashchange，一提hash前端GG、MM们都不稀奇，但是hashchange就鲜有人知了

在一次面试过程中面试官问道这么样实现ajax回退，这个问题当时闷了，下面附上具体代码，以备后用：

    <div id="nihao"></div>
    <button>change</button>

var i=0,url;
    
    var show = function(num) {
        if (num == 0) {
            url = "data/data_1.json";
        } else if (num == 1) {
            url = "data/data_2.json";
        }
        $.get(url,{"cache":false},function(result) {
            $("#nihao").text(result.code);
        },"json");
    };
    
    if(window.attachEvent) {
        window.attachEvent("onhashchange",function(e) {
            var hash = parseInt(window.location.hash.substring(1,2),10);
            show(hash);
        });
    } else if(window.addEventListener) {
        window.addEventListener("hashchange",10);
            show(hash);
        },false);
    }
    
    $("button").click(function() {
        
        if(i == 1) {
            window.location.hash = i--;
        } else if(i == 0) {
            window.location.hash = i++;
        }
    });