TypeError: Person.greet is not a function

Question

function Person(name, age, greet) { 
  this.name = 'Josh';
  this.age = 15;
  this.greet = function(greeting) {
   console.log('Hello I am ', this.name)
  }
}

Person.greet();

我试图让控制台显示“你好，我是 Josh”，但我收到同样的错误消息 Person.greet 不是一个函数

Answer 1

这似乎是一个构造函数，而不是一个对象，因此，您需要在调用方法之前调用new创建构造函数的实例。

// on a side note, if you're not going to use the arguments, better remove them altogether
function Person(name, age, greet) { 
  this.name = 'Josh';
  this.age = 15;
  this.greet = function(greeting) {
   console.log('Hello I am ', this.name)
  }
}

const person = new Person();
person.greet();

Answer 2

function Person(name, age, greet) { 
  this.name = name;
  this.age = age;
  this.greet = function(greeting) {
   console.log('Hello I am', this.name)
  }
}

const max = new Person();
max.name = 'max';
max.age = 18;
max.greet(); // Hello I am max

I realised that I was using a factory function, I was meant to create an object using the new keyword

TypeError: Person.greet is not a function

TypeError: Person.greet is not a function

javascript

constructor