SOURCE

function app(str) {
  var json = JSON.parse(str, function(k, v) {
    if (k === '') return v;
    if (typeof v === 'number') return v * 2;
    return v;
  });
  document.body.innerText = JSON.stringify(json, null, 2);
}

var obj = {
  xian: {
    huawei: 200,
    apple: 10
  },
  beijing: {
    huawei: 300,
    apple: 50
  },
  title: 'hello'
};

app(JSON.stringify(obj));