实例代码“Ctrl+/”提示“F11/ESC”全屏 返回 格式化 恢复 运行
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<!DOCTYPE html>
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<html>
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<head>
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    <title>Accessor Properties Example</title>
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    <script type="text/javascript">
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​
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        var book = {
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            _year: 2004,
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            edition: 1
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        };
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        Object.defineProperty(book, "year", {
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            get: function(){
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                return this._year;
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            },
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            set: function(newValue){
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                if (newValue > 2004) {
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                    this._year = newValue;
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                    this.edition += newValue - 2004;
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                }
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            }
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        });
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        book.year = 2005;
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        alert(book.edition);   //2
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​
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    </script>
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</head>
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<body>
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    <p>Note: this example only works in browsers that have implemented the ECMAScript 5 <code>Object.defineProperty()</code> method (IE9 and Firefox 4).</p>
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</body>
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</html>