console 命令行工具 X clear
console
<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
    <script>
        //赋值四个数
        var arr = [1, 2, 3, 4];

        function getMax()
        {
            var max=arr[0];
            //给max赋值了arr[0],从arr[1]开始比较减少计算
            for(i=1;i<4;i++)
            {
                max=(max>arr[i])?max:arr[i];
            }
            return max;
        }
        document.write(getMax());
    </script>
</head>
<body>
</body>
</html>