chrome extendsion 储存

    var username =document.getElementById("username").value;    var password =document.getElementById("password").value;    if (!username) {        return false;    }    if (!password) {        return false;    }    /*    localStorage.username=username;    localStorage.password = password;    */    chrome.storage.sync.set({un: username}, function() {  });    chrome.storage.sync.set({ps: password}, function() {  });    return true;}

    chrome.storage.sync.get(null,function(obj){       var j= JSON.stringify(obj);       //  alert(j);        console.log(j);       user = obj.un;        console.log(user);       psd = obj.ps;        console.log(psd);    });