What is the method for retrieving a class's property without creating an object instance?

Question

What is the method for retrieving a class's property without creating an object instance?

Currently, I am working with a class setup like this:

class MyClass {
  constructor(privateInfo) {
    this.a = "a";
    this.b = "b";
  }

  myMethod() {
    return privateInfo;
  }
}

It seems that the privateInfo variable needs to be accessed, but it is not defined in the constructor.

Using private properties is not an option, as the property will be included in the stringified object which is not desired.

Is there a way to work around this? Any hints or suggestions would be greatly appreciated.

javascript

Answer 1

Answer №1

Using private properties wouldn't be effective because when the object is stringified, the property still appears in the string.

Actually, it does work:

class MyClass {
  #c;
  constructor(c) {
    this.a="a";
    this.b="b";
    this.#c=c;
  }
  myMethod() {
    return this.#c;
  }
}
const obj = new MyClass('hi');
console.log(JSON.stringify(obj));
console.log(obj.myMethod());

Another approach is to create the method within the constructor as a closure over the c variable:

class MyClass {
  constructor(c) {
    this.a="a";
    this.b="b";
    this.myMethod = () => {
      return c;
    };
  }
}
const obj = new MyClass('hi');
console.log(JSON.stringify(obj));
console.log(obj.myMethod());

Other solutions that work with regular properties and prevent them from being included in the JSON.stringify output include making the property non-enumerable or defining a custom toJSON method.

Answer 2

Using private properties wouldn't be effective because when the object is stringified, the property still appears in the string.

Actually, it does work:

class MyClass {
  #c;
  constructor(c) {
    this.a="a";
    this.b="b";
    this.#c=c;
  }
  myMethod() {
    return this.#c;
  }
}
const obj = new MyClass('hi');
console.log(JSON.stringify(obj));
console.log(obj.myMethod());

Another approach is to create the method within the constructor as a closure over the c variable:

class MyClass {
  constructor(c) {
    this.a="a";
    this.b="b";
    this.myMethod = () => {
      return c;
    };
  }
}
const obj = new MyClass('hi');
console.log(JSON.stringify(obj));
console.log(obj.myMethod());

Other solutions that work with regular properties and prevent them from being included in the JSON.stringify output include making the property non-enumerable or defining a custom toJSON method.

Answer 3

Answer №2

Utilizing the `static` Keyword :

Official MDN Explanation :

When it comes to static properties, they are not accessible directly on instances of the class. Instead, they are accessed on the class itself.

Static methods are commonly used as utility functions, like those for creating or duplicating objects. On the other hand, static properties are beneficial for caches, fixed configurations, or any other data that doesn't need to be duplicated across instances.

Illustrative Instance

class Student {
  name: string;
  static age: number;
  constructor(age: number) {
    this.name = 'John';
    Student.age = age;
  }
  static getAge = () => Student.age;
}

const student = new Student(20);

const json = JSON.stringify(student); // {"name":"John"}
console.log(json);
console.log(Student.getAge()); // 20

Your Implementation:

class MyClass {
  a: string;
  b: string;
  static c: string;
  constructor(c:string) {
    this.a = 'a';
    this.b = 'b';
    MyClass.c = c;
  }
  myMethod() {
    return MyClass.c;
  }
}
const obj = new MyClass('hello'); 
console.log(JSON.stringify(obj)); // {"a":"a","b":"b"}
console.log(obj.myMethod()); // hello

Answer 4

Utilizing the `static` Keyword :

Official MDN Explanation :

When it comes to static properties, they are not accessible directly on instances of the class. Instead, they are accessed on the class itself.

Static methods are commonly used as utility functions, like those for creating or duplicating objects. On the other hand, static properties are beneficial for caches, fixed configurations, or any other data that doesn't need to be duplicated across instances.

Illustrative Instance

class Student {
  name: string;
  static age: number;
  constructor(age: number) {
    this.name = 'John';
    Student.age = age;
  }
  static getAge = () => Student.age;
}

const student = new Student(20);

const json = JSON.stringify(student); // {"name":"John"}
console.log(json);
console.log(Student.getAge()); // 20

Your Implementation:

class MyClass {
  a: string;
  b: string;
  static c: string;
  constructor(c:string) {
    this.a = 'a';
    this.b = 'b';
    MyClass.c = c;
  }
  myMethod() {
    return MyClass.c;
  }
}
const obj = new MyClass('hello'); 
console.log(JSON.stringify(obj)); // {"a":"a","b":"b"}
console.log(obj.myMethod()); // hello

Answer 5

Answer №3

In my practical course, I introduced the attributes:

class MyClass{

  //other attributes
  preQ: string;
  postQ: string;

  constructor(data: InputData = { cli: cli.flags }) {
    Object.defineProperties(this, {
      preQ: { enumerable: false },
      postQ: { enumerable: false },
    });
    // other things
 }
}

As mentioned in the initial comment by Pointy. These attributes do not show up in the output of JSON.stringify.

These attributes are not meant to be transmitted to the server.

Answer 6

In my practical course, I introduced the attributes:

class MyClass{

  //other attributes
  preQ: string;
  postQ: string;

  constructor(data: InputData = { cli: cli.flags }) {
    Object.defineProperties(this, {
      preQ: { enumerable: false },
      postQ: { enumerable: false },
    });
    // other things
 }
}

As mentioned in the initial comment by Pointy. These attributes do not show up in the output of JSON.stringify.

These attributes are not meant to be transmitted to the server.

What is the method for retrieving a class's property without creating an object instance?

Answer №1

Answer №2

Utilizing the `static` Keyword :

Illustrative Instance

Your Implementation:

Answer №3

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What is the method for retrieving a class's property without creating an object instance?

Answer №1

Answer №2

Utilizing the static Keyword :

Illustrative Instance

Your Implementation:

Answer №3

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Utilizing the `static` Keyword :