代码取决于您正在侦听的事件，通过使用 JavaScript 事件KeyCode测试页面 here 与测试输入，例如为了完全停止（。左移右移），您有

  onKeyDown onKeyPress onKeyUp 
 event.keyCode 190 46 190 
 event.charCode 0 46 0 
 event.which 190 46 190 
 $ p $对于数字键盘上的。，它是 
 

  onKeyDown onKeyPress onKeyUp 
 event.keyCode 110 46 110 
 event.charCode 0 46 0 
 event.which 110 46 110 
$如您所见，使用 charCode 检查 onKeyPress 是最为一致的。   >这是unicode号码; 使用String.fromCharCode（46）; //。。 

有一个  MDN页面上的完整列表，用于 KeyboardEvent      


 
 注意：Web开发人员不应在keydown和keyup事件处理程序中使用可打印键的keycode属性。如上所述，键码不能用于检查将要输入的字符，特别是当按下Shift键或AltGr键时。当Web开发人员实现快捷键处理程序时，keypress事件至少在Gecko上是更好的事件。详情请参阅 Gecko按键事件。
 


您可以观察在 keyCode 上使用 AltGr 或 Shift 我也链接到测试页面。
 
I've limited the input field to only numbers through js but am not sure how to also allow decimals...
function isNumberKey(evt)
      {
         var charCode = (evt.which) ? evt.which : event.keyCode
         if (charCode > 31 && (charCode < 48 || charCode > 57))
            return false;

         return true;
      }

Thank you in advance!

Answer:
function isNumberKey(evt)
 {
 var charCode = (evt.which) ? evt.which : event.keyCode
 if (charCode > 31 && (charCode < 48 || charCode > 57) && charCode != 46)
    return false;

 return true;
 }

Adding the charCode 46 worked perfectly (keypress value). 190 and 110 did nothing.

Thanks for your help all!

Codes depend on which event you're listening to, an easy way to find what you want is by using the JavaScript Event KeyCode Test Page here with test input, e.g. for a full stop (the . left of right shift) you have
               onKeyDown    onKeyPress    onKeyUp
event.keyCode        190            46        190
event.charCode         0            46          0
event.which          190            46        190

and for the . on the numeric pad it is
               onKeyDown    onKeyPress    onKeyUp
event.keyCode        110            46        110
event.charCode         0            46          0
event.which          110            46        110

As you can see, it is most uniform to check with onKeyPress with charCode which is it's unicode number; String.fromCharCode(46); // ".".

There is a full list on the MDN page for KeyboardEvent where it is also stated

  
Note: Web developers shouldn't use keycode attribute of printable keys in keydown and keyup event handlers. As described above, keycode is not usable for checking character which will be inputted especially when Shift key or AltGr key is pressed. When web developers implement shortcut key handler, keypress event is better event for that purpose on Gecko at least. See Gecko Keypress Event for the detail.

You can observe the strange effects of using AltGr or Shift on keyCode with the key of choice in the test page I linked to as well.