How can one effectively incorporate a 'toJson' function in TypeScript?

Question

How can one effectively incorporate a 'toJson' function in TypeScript?

Does anyone know the best approach for adding a toJson function to a custom class? I've considered implementing functions like Foo.toJson, Foo.toJsonObject, or Foo.jsonify.

Some examples suggest using a serializer. Is that necessary, or is there a more standard way of achieving this functionality?

I want to be able to use the following code:

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

Additionally, for database connection purposes, I also need to manually create a json representation:

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

javascript typescript

Answer 1

Answer №1

If you are unable to directly modify the original class, one way to accomplish this is by following these steps:

Create a new data type that includes the toJSON method in addition to the properties of the original type
Typecast the object to the newly created data type
Assign the required toJSON method to the object

Here's an example demonstrating this concept:

class Bar {
    public number: number;

    constructor(number: number) {
        this.number = number;
    }

    display() {
        console.log(this.number);
    }
}

type ExtendedBar = Bar & {
    toJSON: () => string;
}

const y = new Bar(42);

(y as ExtendedBar).toJSON = function () {
     return `"Number(${this.number})"`
}

y.display();
console.log(y);

Answer 2

If you are unable to directly modify the original class, one way to accomplish this is by following these steps:

Create a new data type that includes the toJSON method in addition to the properties of the original type
Typecast the object to the newly created data type
Assign the required toJSON method to the object

Here's an example demonstrating this concept:

class Bar {
    public number: number;

    constructor(number: number) {
        this.number = number;
    }

    display() {
        console.log(this.number);
    }
}

type ExtendedBar = Bar & {
    toJSON: () => string;
}

const y = new Bar(42);

(y as ExtendedBar).toJSON = function () {
     return `"Number(${this.number})"`
}

y.display();
console.log(y);

How can one effectively incorporate a 'toJson' function in TypeScript?

Answer №1

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