javascript：為什么代碼不起作用

Question

首先，這是我的 javascript 代碼

<script type="text/javascript">
var book = {};

Object.defineProperties(book, {
    _year : {
        value : 2004
    },

    edition : {
        value : 1
    },

    year : {
        get : function () {
            return this._year;
        },

        set : function (newValue) {
            if (newValue > 2004) {
                this._year = newValue;
                this.edition += newValue - 2004;
            }
        }
    }

});

book.year = 2005;
alert(book.edition);
alert(book._year);

誰能幫幫我，我很困惑，謝謝

Answer 1

根據https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperties，您的基礎屬性不可writable

下面的作品：

 var book = {}; Object.defineProperties(book, { _year: { value: 2004, writable: true }, edition: { value: 1, writable: true }, year: { get: function() { return this._year; }, set: function(newValue) { if (newValue > 2004) { this._year = newValue; this.edition += newValue - 2004; } } } }); book.year = 2006; console.log(book.edition); console.log(book._year);