如何從構造函數中訪問原型對象？

Question

如何從構造函數中訪問原型對象？

在以下Javascript代碼中，我有一個Person構造函數，該函數帶有兩個getter / setter函數，以及在其原型內定義的hydrate函數：

+++++++++++++++++++++++++++++
+          Person           +
+++++++++++++++++++++++++++++
+ setFirstname( firstname ) +
+ getFirstname()            +
+ setLastname( lastname )   +
+ getLastname()             +
+++++++++++++++++++++++++++++

+++++++++++++++++++++++++++++
+     Person.prototype      +
+++++++++++++++++++++++++++++
+ hydrate( person )         +
+++++++++++++++++++++++++++++

我想從Person構造函數中調用hydrate（）函數，即使這對我來說沒有意義，就像在完全創建對象之前調用方法，對嗎？ 如果我錯了糾正我。 JavaScript代碼：

function Person( person ) {
    var _firstname = '',
        _lastname ='';

    if ( person ) this.hydrate( person );

    function setFirstname( firstname ) {
        _firstname = firstname;
    }

    function getFirstname() {
        return _firstname;
    }

    function setLastname( lastname ) {
        _lastname = lastname;
    }

    function getLastname() {
        return _lastname;
    }

    this.setFirstname = setFirstname;
    this.getFirstname = getFirstname;

    this.setLastname = setLastname;
    this.getLastname = getLastname;
}

Person.prototype = {

    hydrate: function( person ) {
        this.setFirstname( person.firstname );
        this.setLastname( person.lastname );
    }

};


var john = new Person( {
    firstname: "John",
    lastname: "Doe"
} );

結果：

錯誤：未捕獲的TypeError：this.setFirstname不是函數

問題：我應該怎么做？ 那有可能嗎？

Answer 1

為了做到這一點，我應該更改了hydrate（）函數的調用位置，並將其一直放置在底部[在setFirstname（）和setLastname（）公開可用之后），如下所示：

function Person( person ) {
    var _firstname = '',
        _lastname ='';


    function setFirstname( firstname ) {
        _firstname = firstname;
    }

    function getFirstname() {
        return _firstname;
    }

    function setLastname( lastname ) {
        _lastname = lastname;
    }

    function getLastname() {
        return _lastname;
    }

    this.setFirstname = setFirstname;
    this.getFirstname = getFirstname;

    this.setLastname = setLastname;
    this.getLastname = getLastname;

    if ( person ) this.hydrate( person );

}

Person.prototype = {

    hydrate: function( person ) {
        this.setFirstname( person.firstname );
        this.setLastname( person.lastname );
    }

};


var john = new Person( {
    firstname: "John",
    lastname: "Doe"
} );