<body>
<input type="text" placeholder="只能输入数字">
<script src="https://libs.baidu.com/jquery/2.1.4/jquery.min.js"></script>
<script>
$("input").on("input",function(){
var result=$(this).val();
result=result.replace(/D/g,"");
$(this).val(result)
});
</script>
</body>