为什么要使用使用.this(JavaScript)的方法，需要在对象(构造函数)中调用该函数?

问题描述

var setAge = function (newAge) {
  this.age = newAge;
};
// now we make bob
var bob = new Object();
bob.age = 30;
bob.setAge = setAge;
bob.setAge(50);
console.log(bob.age);

这可行，但是当我尝试这样做

This works, but when I try to do this

var setAge = function (newAge) {
  this.age = newAge;
};
var bob = new Object();
bob.age = 30;
bob.setAge(50);
console.log(bob.age);

在编译器中返回"bob.setAge()不是函数"吗?

it returns "bob.setAge() is not a function" in the compiler?

推荐答案

您已经创建了一个对象'Bob'，但是在分配该对象之前，该对象没有方法'setAge'.

You have created an object 'Bob', but that object does not have the method 'setAge' until you assign it.

您可能要考虑在设计中做类似的事情:

You may want to look into doing something like this in your design:

function Person(){
this.age = 30;
this.setAge = function(age){
 this.age = age;
 return this;
}
}

var bob = new Person;
bob.setAge(20);
console.log(bob.age);

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