How to calculate age on Class when creating an instance

November 13, 2022

I would like to automatically calculate and set an age when creating an instance.
I made a function that calculates and returns an age.
It works, but I wonder if it’s possible to write the function/method in the Member Class without using the global space.

class Member {
  static id = 0;

  constructor(firstName, lastName, birthDay) {
    Member.id++;
    this.id = Member.id;
    this.firstName = firstName;
    this.lastName = lastName;
    this.birthDay = birthDay;
    this.age = getAge(birthDay);
  }
}

const m1 = new Member('Oliver', 'Cruz', '11/13/1990');
console.log('m1:', m1.age); // 32 (as of Nov 13rd, 2022)

const m2 = new Member('Sophia', 'Brown', '11/30/1992');
console.log('m2:', m2.age); // 29 (as of Nov 13rd, 2022)

/**
 * Calculate age function
 * @param {String} birthDay - ex '11/13/1990'
 * @returns {Number} - age
 */
function getAge(birthDay) {
  const now = new Date();
  const bd = new Date(birthDay);
  const diff = now - bd;
  const age = new Date(diff).getFullYear() - 1970;

  return age;
}

>Solution :

You can add it as a static method on the Member class.

class Member {
  static id = 0;

  constructor(firstName, lastName, birthDay) {
    Member.id++;
    this.id = Member.id;
    this.firstName = firstName;
    this.lastName = lastName;
    this.birthDay = birthDay;
    this.age = Member.getAge(birthDay);
  }

  /**
   * Calculate age function
   * @param {String} birthDay - ex '11/13/1990'
   * @returns {Number} - age
   */
  static getAge = (birthDay) => {
    const now = new Date();
    const bd = new Date(birthDay);
    const diff = now - bd;
    const age = new Date(diff).getFullYear() - 1970;

    return age;
  }
}

const m1 = new Member('Oliver', 'Cruz', '11/13/1990');
console.log('m1:', m1.age); // 32 (as of Nov 13rd, 2022)

const m2 = new Member('Sophia', 'Brown', '11/30/1992');
console.log('m2:', m2.age); // 29 (as of Nov 13rd, 2022)