Use setter to validate parameter in constructor

Question

Javascript

Can setter used to validate parameter when creating new object, as seen on this code, the string input on numberOfStudents bypass the setter

class School {
  constructor(name, level, numberOfStudents) {
    this._name = name;
    this._level = level;
    this._numberOfStudents = numberOfStudents;
  }

  get numberOfStudents() {
    return this._numberOfStudents;
  }

  set numberOfStudents(value) {
    if (isNaN(value)) {
      console.log('Invalid input: numberOfStudents must be set to a Number.');
    } else {
      return (this._numberOfStudents = value);
    }
  }
}

const primaryOne = new School('Primary One', 'L1', 'ten');

prints

School { _name: 'Primary One', _level: 'L1', _numberOfStudents: 'ten' }

Please help

Answer 1

You're bypassing the validation because you're assigning to the internal _numberOfStudents property. The setter is only run when you assign to numberOfStudents. So change the constructor to do that:

class School {
  constructor(name, level, numberOfStudents) {
    this._name = name;
    this._level = level;
    this.numberOfStudents = numberOfStudents;
  }

  get numberOfStudents() {
    return this._numberOfStudents;
  }

  set numberOfStudents(value) {
    if (isNaN(value)) {
      console.log('Invalid input: numberOfStudents must be set to a Number.');
    } else {
      this._numberOfStudents = value;
    }
  }
}

const primaryOne = new School('Primary One', 'L1', 'ten');