js--prompt对话框

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>prompt</title>
    <script>
        function rec() {
            var score;
            score =prompt("请输入你的成绩，1-100数值之间");
            if(score>90){
                document.write("好棒啊");
            }
            else if(score>=75){
                document.write("不错哦");
            }
            else if(score>=60){
                document.write("及格了");
            }
            else if(score<60&&score>=0){
                document.write("加油吧");
            }
            else{
                document.write("请输入正确数值");
            }
        }
    </script>
</head>
<body>
<input type="button" name="button" onClick="rec()" value="点击我，对成绩做评价">
</body>
</html>