一个封装了localStorage的增删改查的方法

localStorage的增删改查都其实比较简单，每次需要判断浏览器是否禁用，这挺麻烦的；

而且没有像COOKIE一样的，自动过期时间，长期下去会有垃圾数据在里面；我们知道android的系统只支持5M存储空间，iphone是10MB，一旦超过限制会提示用户，甚至报错。

一、包含一下功能：

1、定时清理localStorage;

2、支持过期时间;

3、检测浏览器是否禁用localStorage;

二、顺便贴一个COOKIE的存取方法，接口类似：

(function($){
    /*
     * $.cookie('name', 'test',{expires: 7});  //设置  
     * 
     * */
    $.cookie = function(name, value, options) {
        if (typeof value != 'undefined') {
                  options = options || {};
                  if (value === null) {
                            value = '';
                            options = $.extend({}, options);
                            options.expires = -1;
                  }
                  var expires = '';
                  if (options.expires && (typeof options.expires == 'number' || options.expires.toUTCString)) {
                            var date;
                            if (typeof options.expires == 'number') {
                                      date = new Date();
                                      date.setTime(date.getTime() + (options.expires * 24 * 60 * 60 * 1000));
                            } else {
                                      date = options.expires;
                            }
                            expires = '; expires=' + date.toUTCString();
                  }
                  var path = options.path ? '; path=' + (options.path) : '';
                  var domain = options.domain ? '; domain=' + (options.domain) : '';
                  var secure = options.secure ? '; secure' : '';
                  document.cookie = [name, '=', encodeURIComponent(value), expires, path, domain, secure].join('');
                  return this;
            } else {
                  var cookieValue = null;
                  if (document.cookie && document.cookie != '') {
                            var cookies = document.cookie.split(';');
                            for (var i = 0; i < cookies.length; i++) {
                                  var cookie = cookies[i].trim();
                                  if (cookie.substring(0, name.length + 1) == (name + '=')) {
                                            cookieValue = decodeURIComponent(cookie.substring(name.length + 1));
                                            break;
                                  }
                            }
                  }
                  return cookieValue;
        }
    };
    /*
     * 
     * $.localStorage('test') //get
     * $.localStorage('test',123) //set
     * $.localStorage('test',{value:123}) //set
     * $.localStorage('test',{value:123}, 1) //set
     * $.localStorage('test',null) //remove
     * 
     */
    var isCache=true,
        minutes =  1000*60,
        now = Date.now();
    
        try {
              localStorage.setItem('cache','test');
        } catch (e) {
            isCache= false;
        }
    
    resetCache = function(time){//定时清理
        if(!isCache)
            return ;
        var expires, day= minutes*60*24;
        time = time || 0;
        if((expires=localStorage.getItem('_expires')) && expires>now){
            return false;
        }
        
        var len= localStorage.length,item,key,t;
        for(var i=0; i<len; i++){
            key= localStorage.key(i);
            item=localStorage.getItem(key);

            
            if(item && item.indexOf('_expires')!=-1){
                t=item.match(/_expires":(\d+)/)[1];
                if(now<t){
                    continue;
                }
            }
            localStorage.removeItem(key);
        }

        
        return localStorage.setItem('_expires', day*time);
    }
          
    resetCache(60);    //2个月检测一遍

    


    $.localStorage = function(name, value, time) {    
        if(!isCache)
            return false;
        
        
        if (typeof value != 'undefined') {    //set
            
            if(value===null){
                return localStorage.removeItem(name);
            }
            
            if(!isNaN(+time)){
                value = {value: value, _expires : now+time*minutes};
            }
            
            localStorage.setItem(name,JSON.stringify(value));  
            
            return value.value || value;
            
         }else{        //get
                var localValue = null,st,et;
                localValue = localStorage.getItem(name);
                
                    try {
                        localValue = JSON.parse(localValue);
                } catch (e) {
                    return localValue;
                }
                
                if($.isObject(localValue) && (et=localValue._expires) ){
                    if(now > et){
                        localStorage.removeItem(name);
                        localValue=null;
                    }else{
                        localValue =  localValue['value'];
                    }
                }
                 return localValue;
        }
    };
})(Zepto);