javascript函数无法访问对象的私有成员

Question

My code is as shown below:

function Person (firstName,lastName,age){
    var firstName = firstName;
    var lastName = lastName;
    var age = age;

    function getName(){
        return firstName+ " " + lastName;
    }
}



var person = new Person("m","t",297)

print(person.getName())

When I run this code, it gives me the following error:

TypeError: person.getName is not a function

Answer 1

use console.log instead of print and don't forget to attach functions to objects using this. notation

 function Person (firstName,lastName,age){ var firstName = firstName; var lastName = lastName; var age = age; this.getName = function(){ return firstName+ " " + lastName; } } var person = new Person("m","t",297) console.log(person.getName())

Answer 2

try replacing it with this.getName

 function Person(firstName, lastName, age) { var firstName = firstName; var lastName = lastName; var age = age; this.getName = function() { return firstName + " " + lastName; } } var person = new Person("m", "t", 297) console.log(person.getName())

ALternatively you can add getName to it's prototype

 function Person(firstName, lastName, age) { this.firstName = firstName; this.lastName = lastName; this.age = age; } Person.prototype.getName = function() { return this.firstName + " " + this.lastName; } var person = new Person("m", "t", 297) console.log(person.getName())

Answer 3

You need to construct by using this so that your instance can get it's own params:

function Person (firstName,lastName,age){
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;

    this.getName = function() {
        return this.firstName+ " " + this.lastName;
    }
}

Answer 4

first of all, for function constructors you use this :

function Person (firstName,lastName,age){
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;

    this.getName = function(){
        return this.firstName+ " " + this.lastName;
    }
}
var me = new Person('m', 't', 297)
console.log(me.getName()) //'m t'

Second, get used to using ES6 classes:

class Person {
  constructor(name, last, age) {
    this.name = name;
    this.last = last;
    this.age = age;
  };

  getName() {
    return `${this.name} ${this.last}` //using ES6 string template literal
  }
}

I think your lacking basics, do personal research before asking on StackOverflow.