为什么我的代码中始终使用UpperCase？

问题描述

<script type="text/javascript" src="jquery-1.3.2.js"></script>
<input id=a type="text" value='sss'/>
<script type="text/javascript">
    $('#a').keyup(
  function(event){
   alert(String.fromCharCode(event.which))
  })
</script>

您可以在浏览器中测试此代码，

you can test this code in your brower,

它总是提醒TopCase一个charcode。

and it always alert UpperCase of a charcode.

推荐答案

起初我认为这是一个bug，因为预期的小写返回 keypress 事件的值。事实证明，在 keyup / keydown 上，始终返回密钥的ASCII大写/非移位版本。

At first I thought this was a bug, as the expected lowercase value is returned for the keypress event. It turns out that on keyup/keydown the ASCII uppercase/non-shifted version of a key is always returned.

从以下链接：

• 按Shift + a算作单个按键 event。


• 当按下键时，按Shift + a计为两个 keydown 事件，两个 keyup 释放密钥时的事件。


• keypress 返回复合一致按下一个或多个键的值。


• keydown 和 keyup 返回单键的值，同时忽略任何组合键。


• Pressing Shift+a counts as a single keypress event.
• Pressing Shift+a counts as two keydown events when the keys are pressed down and two keyup event when the keys are released.
• keypress returns the composite value of one or more keys being pressed in unison.
• keydown and keyup return the value of a single key while ignoring any key combinations.

现在这里有一个令人困惑的部分：由于某种原因，的未移位值 key作为键代码65返回。但是65表是ASCII表中的大写A.所以沿着这条线的某个地方，浏览器采用小写字母a（ASCII代码97），将其转换为大写字母A，然后将 keydown / keyup 作为非移位字符传递。很奇怪，不是吗？

Now here's the confusing part: for some reason the unshifted value of the a key is returned as key code 65. But 65 is uppercase A in the ASCII table. So somewhere along the line the browser is taking the lowercase a (ASCII code 97), transforming it to uppercase A, then passing it keydown/keyup as the non-shifted character. Weird, isn't it?

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