How to issue an error if there is undefined?-CodePudding

"use strict";

class Student {

  #
  name;#
  age;#
  city;#
  programmings;#
  os;


  constructor(name, age, city, programmings, os) {

    this.#name = name;
    this.#age = age;
    this.#city = city;
    this.#programmings = programmings;
    this.#os = os;

  }


  get getName() {

    let hiddenName = '';
    for (let i = 0; i < this.#name.length; i  ) {
      hiddenName  = '*';
    }
    return 'Student name is '   hiddenName;
  }


  get getAge() {

    let hiddenAge = '';
    let ageToString = this.#age.toString();

    for (let i = 0; i < ageToString.length; i  ) {
      hiddenAge  = '*';
    }
    return 'Student age is '   hiddenAge;
  }

  get getCity() {

    let hiddenCity = '';
    for (let i = 0; i < this.#city.length; i  ) {
      hiddenCity  = '*';
    }
    return 'Student city is '   hiddenCity;
  }

  get getProgrammings() {

    let hiddenProgrammings = '';
    for (let i = 0; i < this.#programmings.length; i  ) {
      hiddenProgrammings  = '*';
    }
    return 'Student programmings is '   hiddenProgrammings;
  }

  get getOs() {

    let hiddenOs = '';
    for (let i = 0; i < this.#os.length; i  ) {
      hiddenOs  = '*';
    }
    return 'Student os is '   hiddenOs;
  }

}


const student = new Student('Ivan', 33, 'Moscow', 'Java', 'Windows');


console.log(student.name);

When accessing any field of an object, the result is directly output "undefined". How to make it so that when accessing the object fields directly, an error is issued, the text of which I will write myself

for example: console.log(student.name);

output: 'Information is private'

CodePudding user response：

Try this:

console.log(student.name ?? 'Information is private');

?? is an IF statement but in shorter way.

It means if the value is set, the value is true and the value in the left side must be shown, but if the value is not set, the value at the left side must be shown.

CodePudding user response：

student.name calls get name() not get getName()

"use strict";
class Student {
    #name;
    #age;
    #city;
    #programmings;
    #os;

    constructor(name, age, city, programmings, os) {
        this.#name = name;
        this.#age = age;
        this.#city = city;
        this.#programmings = programmings;
        this.#os = os;
    }

    get name() {
        return typeof this.#name === "undefined" ? "Information is private" : this.#name;
    }

    get getName() {
        let hiddenName = "";
        for (let i = 0; i < this.#name.length; i  ) {
            hiddenName  = "*";
        }
        return "Student name is "   hiddenName;
    }

    get getAge() {
        let hiddenAge = "";
        let ageToString = this.#age.toString();

        for (let i = 0; i < ageToString.length; i  ) {
            hiddenAge  = "*";
        }
        return "Student age is "   hiddenAge;
    }

    get getCity() {
        let hiddenCity = "";
        for (let i = 0; i < this.#city.length; i  ) {
            hiddenCity  = "*";
        }
        return "Student city is "   hiddenCity;
    }

    get getProgrammings() {
        let hiddenProgrammings = "";
        for (let i = 0; i < this.#programmings.length; i  ) {
            hiddenProgrammings  = "*";
        }
        return "Student programmings is "   hiddenProgrammings;
    }

    get getOs() {
        let hiddenOs = "";
        for (let i = 0; i < this.#os.length; i  ) {
            hiddenOs  = "*";
        }
        return "Student os is "   hiddenOs;
    }
}

const student = new Student("Ivan", 33, "Moscow", "Java", "Windows");

console.log(student.name);