"undefined"in Object.defineProperty in Constructor

Question

firstName 및 lastName 메서드의 현재 값을 표시하는 방법을 잘못 이해합니다. 왜냐하면 지금은 존에 오류가 있습니다. 이름과 존.

function User(fullName) { 
    this.fullName = fullName.split(' '); 

    Object.defineProperty(this, 'firstName', { 
    get: function() { 
     this.firstName = this.fullName[0]; 
     return this.firstName; 
    } 
    }); 

    Object.defineProperty(this, 'lastName', { 
    get: function() { 
     this.lastName = this.fullName[1]; 
     return this.lastName; 
    } 
    }); 

} 

var jone= new User("Jone Coven"); 

console.log(jone.fullName); 
console.log(jone.firstName); 
console.log(jone.lastName); 

Answer 1

문제는 this.firstName = ...이며, 이미 Object.defineProperty(this, ...)를 사용하여 정의 된 속성을 오버라이드 (override) this.lastName = ....

function User(fullName) { 
    this.fullName = fullName.split(' '); 

    Object.defineProperty(this, 'firstName', { 
    get: function() { 
     this._firstName = this.fullName[0]; // <------ _firstName 
     return this._firstName; 
    } 
    }); 

    Object.defineProperty(this, 'lastName', { 
    get: function() { 
     this._lastName = this.fullName[1]; // <----- _lastName 
     return this._lastName; 
    } 
    }); 

} 

var jone= new User("Jone Coven"); 

console.log(jone.fullName); 
console.log(jone.firstName); 
console.log(jone.lastName); 

---

또 다른 해결책은 바로 결과를 반환하는 것입니다 :

function User(fullName) { 
    this.fullName = fullName.split(' '); 

    Object.defineProperty(this, 'firstName', { 
    get: function() { 
     return this.fullName[0]; 
    } 
    }); 

    Object.defineProperty(this, 'lastName', { 
    get: function() { 
     return this.fullName[1]; 
    } 
    }); 

} 

var jone= new User("Jone Coven"); 

console.log(jone.fullName); 
console.log(jone.firstName); 
console.log(jone.lastName); 

---

Answer 2

왜 이렇게 복잡합니까?

function User(fullName) { 
    this.fullName = fullName.split(' '); 
    this.firstName = this.fullName[0]; 
    this.lastName = this.fullName[1]; 
} 

var jone= new User("Jone Coven"); 

Answer 3

function User(fullName) { 
    this.fullName = fullName.split(' '); 
this.firstName = function() { 
     return this.fullName[0]; 

    } 
this.lastName = function() { 
     return this.fullName[1]; 

    } 
} 

var jone= new User("Jone Coven"); 

console.log(jone.fullName); 
console.log(jone.firstName()); 
console.log(jone.lastName());