Backbone LocalStorage Model

backbone.localstorage.js

var StorageBase=Backbone.Model.extend({
  constructor: function(){
    Backbone.Model.apply(this,arguments);

    //check if the storage can be used
    this.supportLocalStorage=!!localStorage;
    this.prefix="lm.v2.";

    var self=this;
    var addPrefix=function(k){
      return self.prefix+k;
    }
    var removePrefix=function(k){
      return k.slice(self.prefix.length);
    };

    //add the data from localStorage
    if(this.supportLocalStorage){
      for(var i=0,len=localStorage.length;i<len;++i){
        var k=localStorage.key(i);
        //check prefix
        if(this.prefix&&k.indexOf(this.prefix)!=0)
          continue;
        var v=localStorage.getItem(k);
        try{
          //try to parse into objects
          v=JSON.parse(v);
        }catch(e){}
        this.set(removePrefix(k),v);
      }
    }else{
      _.each($.cookie,function(v,k){
        this.set(removePrefix(k),v);
      })
    }

    //reset changed prop
    this.changed={};

    this.on("change",function(m){
      UTIL.log("storageObject changed",this.changed);
      if(this.supportLocalStorage){
        _.each(this.changed,function(v,k){
          //add prefix, ready to save
          k=addPrefix(k);
          if(v===null||v===void 0){
            localStorage.removeItem(k);
            return;
          }
          if(_.isObject(v))
            v=JSON.stringify(v);
          localStorage.setItem(k,v);
        });
      }else{
        if(_.isObject(v))
          $.cookie(addPrefix(k),v);
      }
    });
  },
  save: function(key,val,options){
    var attrs;
    if (key==null||_.isObject(key)){
      attrs=key;
      options=val;
    }else{
      (attrs={})[key]=val;
    }
    attrs=attrs||this.attributes;
    this.changed=attrs;
    this.trigger("change",this);
  },
  unset: function(attr,options){
    //Use no 'delete'
    //but QAQ
    this.set(attr,void 0,_.extend({}, options, {unset: true}));
  }
});

var storageObject=new StorageBase();