What is the best way to implement custom serialization for Date types in JSON.stringify()?

Question

What is the best way to implement custom serialization for Date types in JSON.stringify()?

class MyClass {
  myString: string;
  myDate: Date;
}

function foo() {
  const myClassArray: MyClass[] = ....
  return JSON.stringify(myClassArray); // or expressApp.status(200).json(myClassArray);
}

foo will generate a JSON string with the date format of YYYY-MM-DDThh:mm:ssZ.

I am interested in customizing the serialization process for the myDate property when using JSON.stringify().

If altering how JSON.stringify() works is not feasible, I am open to exploring other serialization libraries that might offer more customization options. Perhaps a library implementing a decorator pattern could help achieve this? Or maybe there is a native solution available?

javascript typescript

Answer 1

Answer №1

Utilize the replacer parameter and define a function to achieve this functionality. Here is a simple example:

const data = [{
    date: new Date(),
    id: 1
  },
  {
    date: new Date(),
    id: 2
}]

const originalData = JSON.stringify(data)
const transformedData = JSON.stringify(data, replacer('date'))

function replacer(target) {
  return function(key, value) {
    if (key == target) {
      const month = new Date(value).getMonth()
      return `Date month: ${month}`
    }
    return value
  }
}

// [{"date":"2020-03-20T19:13:11.594Z","id":1},{"date":"2020-03-20T19:13:11.594Z","id":2}]
console.log(originalData)

// [{"date":"Date month: 2","id":1},{"date":"Date month: 2","id":2}]
console.log(transformedData)

Update

If you have any suggestions for improving my TypeScript decorator skills, please share them.

Here's an example of using a decorator:

@transformDate
class MyClass {
  date: Date;
  id: number;

  constructor(date, id) {
    this.date = date;
    this.id = id;
  }
}

function transformDate(target: any) {
  const formatted = new Intl.DateTimeFormat("en", {
    year: "numeric",
    month: "short",
    day: "2-digit"
  }).format(this.date);

  target.prototype.toJSON = function() {
    return {
      ...this,
      date: formatted
    };
  };

  return target;
}

const newData = [new MyClass(new Date(), 1), new MyClass(new Date(), 2)];

// [{"date":"Mar 20, 2020","id":1},{"date":"Mar 20, 2020","id":2}]
console.log(JSON.stringify(newData));

Answer 2

Utilize the replacer parameter and define a function to achieve this functionality. Here is a simple example:

const data = [{
    date: new Date(),
    id: 1
  },
  {
    date: new Date(),
    id: 2
}]

const originalData = JSON.stringify(data)
const transformedData = JSON.stringify(data, replacer('date'))

function replacer(target) {
  return function(key, value) {
    if (key == target) {
      const month = new Date(value).getMonth()
      return `Date month: ${month}`
    }
    return value
  }
}

// [{"date":"2020-03-20T19:13:11.594Z","id":1},{"date":"2020-03-20T19:13:11.594Z","id":2}]
console.log(originalData)

// [{"date":"Date month: 2","id":1},{"date":"Date month: 2","id":2}]
console.log(transformedData)

Update

If you have any suggestions for improving my TypeScript decorator skills, please share them.

Here's an example of using a decorator:

@transformDate
class MyClass {
  date: Date;
  id: number;

  constructor(date, id) {
    this.date = date;
    this.id = id;
  }
}

function transformDate(target: any) {
  const formatted = new Intl.DateTimeFormat("en", {
    year: "numeric",
    month: "short",
    day: "2-digit"
  }).format(this.date);

  target.prototype.toJSON = function() {
    return {
      ...this,
      date: formatted
    };
  };

  return target;
}

const newData = [new MyClass(new Date(), 1), new MyClass(new Date(), 2)];

// [{"date":"Mar 20, 2020","id":1},{"date":"Mar 20, 2020","id":2}]
console.log(JSON.stringify(newData));

What is the best way to implement custom serialization for Date types in JSON.stringify()?

Answer №1

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