JS获取键盘上任意按键的值

<script language="javascript">
  function keyDown()
  {
     var keycode =event.keyCode;
     var keychar=String.fromCharCode(keycode);
     alert('ASCII='+keycode+'\nKeyChar='+keychar);

  }
    document.onkeydown=keyDown;

 

var keycode =event.keyCode;
//    var keychar=String.fromCharCode(keycode);
//    alert('ASCII='+keycode+'\nKeyChar='+keychar);
	//控制该文本框只能输入数字、小数点、退格键
	//数字：48-57 96-105 小数点：190、110 退格键：8
	if((keycode>=48&&keycode<=57)||(keycode>=96&&keycode<=105)||(keycode==190)||(keycode==110)||(keycode==8)){
		
	}else{
		event.returnValue = false;
	}