JavaScriot原型语法的问题

[weixin_40980353]

为什么代码这样写就会出现错误呢
function Person() {
Person.prototype= {
name: "Nicholas",
age: 29
}
}

alert(Person.prototype.name);

[LittleMan_LC]

alert() 应写下function 里面。

<script type=text/javascript>
	window.onload=function (){
		Person();
	}
	function Person() {
    Person.prototype= {
        name: "Nicholas",
        age: 29
    }
	alert(Person.prototype.name); 
}
</script>

[weixin_40980353]

引用 1 楼 LittleMan_LC 的回复:

alert() 应写下function 里面。

<script type=text/javascript>
	window.onload=function (){
		Person();
	}
	function Person() {
    Person.prototype= {
        name: "Nicholas",
        age: 29
    }
	alert(Person.prototype.name); 
}
</script>

为什么啊 这个有什么内部原因吗

[天际的海浪]

要在构造函数外设置 prototype，否则就要调用一次构造函数才能设置 function Person() { } Person.prototype= { name: "Nicholas", age: 29 }

[中年转行做前端]

你没执行Person()这个方法，里面的”Person.prototype= “赋值语句还没有执行。

[无聊的上午]

引用 2 楼 weixin_40980353 的回复:

[quote=引用 1 楼 LittleMan_LC 的回复:] alert() 应写下function 里面。

<script type=text/javascript>
	window.onload=function (){
		Person();
	}
	function Person() {
    Person.prototype= {
        name: "Nicholas",
        age: 29
    }
	alert(Person.prototype.name); 
}
</script>

为什么啊 这个有什么内部原因吗 [/quote] 你的写法类似做了个闭包，外部访问不到就报错

[pavee]

Almost every function (with the exception of some built-in functions) has a prototype property that is used during the creation of new instances. prototype solved the problem of inheritance of JavaScript. If you want to define a constructor, using the following format:

function Person(name) {
  this.name = name;
  this.sayName = function () {
    console.log(this.name);
  };
}

or defined as prototypes property:

Person.prototype.profile = {
  name: "Nicholas",
  age: 29
}