如何用Javascript快速搜索JSON？

// JSON数据
var jsonData = {
  "employees": [
    {
      "firstName": "John",
      "lastName": "Doe",
      "age": 30,
      "city": "New York"
    },
    {
      "firstName": "Jane",
      "lastName": "Smith",
      "age": 25,
      "city": "San Francisco"
    }
  ]
};

// 搜索函数
function searchJSON(keyword, json) {
  var results = [];

  function search(obj) {
    for (var key in obj) {
      if (typeof obj[key] === 'string') {
        if (obj[key].indexOf(keyword) !== -1) {
          results.push(obj);
          break;
        }
      } else if (typeof obj[key] === 'object') {
        search(obj[key]);
      }
    }
  }

  search(json);
  return results;
}

// 调用搜索函数
var keyword = "John";
var searchResults = searchJSON(keyword, jsonData);
console.log(searchResults);