how to save html registration form data into json file then login based on it

$('#Myform').attr('onsubmit', 'test()');

function test() {

  var obj = {};

  obj.title =$('#title').prop('value');
  console.log('title: '+obj.title);

  obj.userID =$('#userID').prop('value');
  console.log('userID: '+obj.website);

  obj.passCode =$('#passCode').prop('value').split(',');
  console.log('passCode: '+obj.tags);

  doSomething(JSON.stringify(obj));

}