在 TypeScript 中实现“toJson”function 的正确方法是什么？

Question

I have a custom class, and I need a toJson function. Of course, I can just implement a function called Foo.toJson or Foo.toJsonObject or Foo.jsonify .

But what would be the standard way of doing this? I also saw some examples which include a serializer . Do I need to go that far?

Basically I want to be able to make this work:

const foo = new Foo();
fse.writeJson('file.json', foo);

But for a database connection I also need to be able to manually create a json representation:

const foo = new Foo();
db.writeObject(foo.toJson());

Answer 1

Assuming you can't just modify the original class:

1. Declare a new type which adds the toJSON method to the original type
2. Cast the object to the new type
3. Assign the toJSON method to it

For example:

class Foo {
    public date: Date;

    constructor(date: Date) {
        this.date = date;
    }

    log() {
        console.log(this.date.toISOString());
    }
}

type ExtendedFoo = Foo & {
    toJSON: () => string;
}

const x = new Foo(new Date);

(x as ExtendedFoo).toJSON = function () {
     return `"\\/Date(${+this.date})\\/"`
}

x.log();
console.log(x);