傳不定參:arguments,參數的個數可變;(例子:css函數)

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <div id="div1" style="width:200px; height:200px; background:red"></div>
  
</body>

<script>

        var oDiv = document.getElementById('div1')

        function css(obj,name,value) {
            if (arguments.length == 2) {
                // 獲取樣式
                return obj.style[name];
            }
            else {
                // 設置樣式
               obj.style[name] = value;
            }
        };
        

        alert(css(oDiv, 'width'))
        
        css(oDiv, 'background' ,'yellow')
</script>

</html>
複製代碼

獲取樣式.png

設置樣式.png
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