can't save the data in the chrome extension storage

Question

I can't save the data that is form data from index.html in the chrome local storage. I also tried to save the data in chrome sync storage but both are not working and already checked my local storage in chrome://extensions but, there were no data.... What should I do for save the data in chrome extension storage?

manifest.json

{
"manifest_version": 2,
"name": "index",
"version": "1.0.0",

"description": "index descript",
"icons": {
  "512": "img/logo.png"
},
"browser_action": {
  "default_icon": {
     "16": "img/logo.png"
  },
  "default_popup": "index.html",
  "default_title": "index",
  "use_navigation_bar": false,
  "mobile_user_agent": true
},

"background": {
    "scripts": [ "js/background.js" ]
},

"permissions": ["tabs", "notifications", "storage"]
}

(function(){
  var  form = document.querySelector('form');
  form.addEventListener('submit', function(evt){
   evt.preventDefault();
   runStorage();
  })
})()

function runStorage() {
 var country = $("#selectCur").val(),
        krw = $("#wantKRW").val(),
        date = $("#pdate").val(),
        arr = [country, krw, date];
   chrome.storage.local.get(['data'], function(res) {
    if(res.data) {
      res.data.push(arr);
      var a = res.data;
   chrome.storage.local.set({ data : a}, function() {
    });
   }
  });
 }