序列化和恢复类实例

你可以使用自定义 toJSON 方法和 reviver 函数以 JSON 格式传输你自己的类的实例。如果对象具有 toJSON 方法，则其结果将被序列化而不是对象本身。

Version < 6

function Car(color, speed) {
  this.color = color;
  this.speed = speed;
}

Car.prototype.toJSON = function() {
  return {
    $type: 'com.example.Car',
    color: this.color,
    speed: this.speed
  };
};

Car.fromJSON = function(data) {
  return new Car(data.color, data.speed);
};

Version >= 6

class Car {
  constructor(color, speed) {
    this.color = color;
    this.speed = speed;
    this.id_ = Math.random();
  }

  toJSON() {
    return {
      $type: 'com.example.Car',
      color: this.color,
      speed: this.speed
    };
  }

  static fromJSON(data) {
    return new Car(data.color, data.speed);
  }
}

var userJson = JSON.stringify({
  name: "John",
  car: new Car('red', 'fast')
});

这将生成一个包含以下内容的字符串：

{"name":"John","car":{"$type":"com.example.Car","color":"red","speed":"fast"}}

var userObject = JSON.parse(userJson, function reviver(key, value) {
  return (value && value.$type === 'com.example.Car') ? Car.fromJSON(value) : value;
});

这会产生以下对象：

{
  name: "John",
  car: Car {
    color: "red",
    speed: "fast",
    id_: 0.19349242527065402
  }
}