input只允许输入数字

function onlyNum(){
  if(!((event.keyCode>=48&&event.keyCode<=57)||(event.keyCode>=96&&event.keyCode<=105)))
    event.returnValue=false;
}

 

 

<input type="text" id="postalcode" name="postalcode" value="" onkeydown="onlyNum();" class="text3" />