//input 限制输入数字和小数
<input type="text" name="demo" value="" onkeyup="if(isNaN(value))execCommand(\'undo\')" onafterpaste="if(isNaN(value))execCommand(\'undo\')"/>

说明: 在input 添加属性
 onkeyup="if(isNaN(value))execCommand(\'undo\')"
 onafterpaste="if(isNaN(value))execCommand(\'undo\')"