do i need a manifest to use localstorage code example

Example: sotre json on chrome storage

var local = (function(){

    var setData = function(key,obj){
        var values = JSON.stringify(obj);
        localStorage.setItem(key,values);
    }

    var getData = function(key){
        if(localStorage.getItem(key) != null){
        return JSON.parse(localStorage.getItem(key));
        }else{
            return false;
        }
    }

    var updateDate = function(key,newData){
        if(localStorage.getItem(key) != null){
            var oldData = JSON.parse(localStorage.getItem(key));
            for(keyObj in newData){
                oldData[keyObj] = newData[keyObj];
            }
            var values = JSON.stringify(oldData);
            localStorage.setItem(key,values);
        }else{
            return false;
        }
    }

    return {set:setData,get:getData,update:updateDate}
})();