看着水了一天的群，终于看到一段高质量的代码了分享一下localStorage

_history : { //缓存
            isLocalStorage:window.localStorage?true:false,
            set : function(key,value){ //设置缓存
                if(this.isLocalStorage){
                    window.localStorage.setItem(key,value);
                }else{
                    var expireDays = 365; //失效时间
                    var exDate=new Date();
                    exDate.setTime(exDate.getTime()+expireDays*24*60*60*1000);
                    document.cookie=key + "=" + escape(value)+";expires=" + exDate.toGMTString();
                }
            },
            read : function(key){ //读取缓存
                if(this.isLocalStorage){
                    return window.localStorage.getItem(key);
                }else{
                    var arr,reg=new RegExp("(^| )"+key+"=([^;]*)(;|$)");
                    if(arr=document.cookie.match(reg)){
                        return unescape(arr[2]);
                    }else{
                        return null;
                    }
                }
            },
            del : function(key){ //删除缓存
                if(this.isLocalStorage){
                    localStorage.removeItem(key);
                }else{
                    var exDate = new Date();
                    exDate.setTime(exDate.getTime() - 1);
                    var read_val=this.read(key);
                    if(read_val!=null) document.cookie= key + "="+read_val+";expires="+exDate.toGMTString();
                }
            }
        },