Display accessor methods when an object is output in TypeScript

Question

Display accessor methods when an object is output in TypeScript

Is there a way in TypeScript/JavaScript to display an object's private properties using their getters instead of the actual property names?

For example, consider this TypeScript class:

class Vehicle {

  constructor(private _brand: string, private _year: number) {}

  get brand(): string {
    return this._brand;
  }

  get year(): number {
    return this._year;
  }

  set year(year: number) {
    this._year = year;
  }

  set brand(brand: string) {
    this._brand = brand;
  }
}

const vehicle: Vehicle = new Vehicle('Toyota', 10);

console.log(vehicle);

Currently, when logging the 'vehicle' object, you would see:

[LOG]: Vehicle: {
  "_brand": "Toyota",
  "_year": 10
}

However, is it possible to achieve a log output like this:

[LOG]: Vehicle: {
  "brand": "Toyota",
  "year": 10
}

javascript typescript oop

Answer 1

Answer №1

The functionality of console.log can vary depending on the environment it's used in. To achieve the specific logging behavior you're looking for, you would need to create your own custom logger function. Here is an example of how such a function could be implemented in JavaScript:

function log(obj) {
    // Retrieve the names of getter properties defined on the prototype
    const ctor = obj.constructor;
    const proto = ctor?.prototype;
    const names = new Set(
        proto
            ? Object.entries(Object.getOwnPropertyDescriptors(proto))
                .filter(([_, {get}]) => !!get)
                .map(([name]) => name)
            : []
    );
    
    // Include the names of "own" properties that do not start with "_"
    for (const name of Object.keys(obj)) {
        if (!name.startsWith("_")) {
            names.add(name);
        }
    }
    
    // Create a simple object containing the values of those properties
    const simple = {};
    for (const name of names) {
        simple[name] = obj[name];
    }
    
    // Check if a "constructor" name exists for the object and include it if available
    let objName =
        obj[Symbol.toStringTag]
        || ctor?.name;
    if (objName) {
        simple[Symbol.toStringTag] = objName;
    }
    
    // Log the simplified object
    console.log(simple);
}

You can test this custom logger function using the live example provided below:

"use strict";

// Sample class definition for testing the log function
class Vehicle {
    constructor(_brand, _year) {
        this._brand = _brand;
        this._year = _year;
    }
    get brand() {
        return this._brand;
    }
    get year() {
        return this._year;
    }
    set year(year) {
        this._year = year;
    }
    set brand(brand) {
        this._brand = brand;
    }
}

// Creating an instance of the Vehicle class
const vehicle = new Vehicle('Toyota', 10);

// Logging the properties of the vehicle object using the log function
log(vehicle);

Feel free to customize and enhance the log function based on your specific requirements and preferences.

Answer 2

The functionality of console.log can vary depending on the environment it's used in. To achieve the specific logging behavior you're looking for, you would need to create your own custom logger function. Here is an example of how such a function could be implemented in JavaScript:

function log(obj) {
    // Retrieve the names of getter properties defined on the prototype
    const ctor = obj.constructor;
    const proto = ctor?.prototype;
    const names = new Set(
        proto
            ? Object.entries(Object.getOwnPropertyDescriptors(proto))
                .filter(([_, {get}]) => !!get)
                .map(([name]) => name)
            : []
    );
    
    // Include the names of "own" properties that do not start with "_"
    for (const name of Object.keys(obj)) {
        if (!name.startsWith("_")) {
            names.add(name);
        }
    }
    
    // Create a simple object containing the values of those properties
    const simple = {};
    for (const name of names) {
        simple[name] = obj[name];
    }
    
    // Check if a "constructor" name exists for the object and include it if available
    let objName =
        obj[Symbol.toStringTag]
        || ctor?.name;
    if (objName) {
        simple[Symbol.toStringTag] = objName;
    }
    
    // Log the simplified object
    console.log(simple);
}

You can test this custom logger function using the live example provided below:

"use strict";

// Sample class definition for testing the log function
class Vehicle {
    constructor(_brand, _year) {
        this._brand = _brand;
        this._year = _year;
    }
    get brand() {
        return this._brand;
    }
    get year() {
        return this._year;
    }
    set year(year) {
        this._year = year;
    }
    set brand(brand) {
        this._brand = brand;
    }
}

// Creating an instance of the Vehicle class
const vehicle = new Vehicle('Toyota', 10);

// Logging the properties of the vehicle object using the log function
log(vehicle);

Feel free to customize and enhance the log function based on your specific requirements and preferences.

Answer 3

Answer №2

It may not be possible to achieve that directly, but one workaround could be defining a log function within the class as shown below:

  logger() {
    console.log({
      make: this.make,
	year: this.year,
    });
  }

You can then execute car.logger();

This will result in an output similar to {make: 'Toyota', year: 10}

Answer 4

It may not be possible to achieve that directly, but one workaround could be defining a log function within the class as shown below:

  logger() {
    console.log({
      make: this.make,
	year: this.year,
    });
  }

You can then execute car.logger();

This will result in an output similar to {make: 'Toyota', year: 10}

Display accessor methods when an object is output in TypeScript

Answer №1

Answer №2

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