javascript - 将方法分配给原型(prototype)不起作用

Question

function Test(){
  this.name = "Hello World";
  function sayName(){
    return this.name;
  }
}
Test.prototype.callName = function(){
    return `Hello my name is, ${this.name}`;
}
const me = new Test();
me.callName();
console.log(me);

输出

Test { name: 'Hello World' }

1. 为什么函数 sayName 不在对象的实例中。
2. 为什么 me.callName() 函数调用不起作用

Answer 1

why is the function sayName is not in the instance of the object.

因为你没有分配它。

this.sayName = sayName;

why is the me.callName() function call is not working

我不知道它对我有用

function Test(){
  this.name = "Hello World";
  this.sayName = function sayName(){
    return this.name;
  }
}
Test.prototype.callName = function(){
    return `Hello my name is, ${this.name}`;
}
const me = new Test();
console.log(me.sayName());
console.log(me.callName());