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javascript – 如何在onkeydown事件处理程序方法中区分大写字母和较低的大写字母

2019-10-08 00:45:37 作者：互联网

<html>
<head>
<title>Test</title>

<script type="text/javascript">

function showChar(e) {
    if (e.keyCode != 16) {
        alert(
           "keyCode: " + e.keyCode + "\n"
          + "SHIFT key pressed: " + e.shiftKey + "\n"
        );
    }
}

</script>
</head>

<body onkeydown="showChar(event);">
<p>Press any character key, with or without holding down
 the SHIFT key.<br /></p>
</body>
</html>

如何在onkeydown事件处理程序方法中区分大写A和小写a？以上算法触发相同的keyCode值.我需要在按下onkeydown时检测大写字母.

注意：代码包含SHIFT键的例外.否则它不允许输入大写字母.顺便说一句,我需要使用onkeydown进行试验.

解决方法:

在我看来,你回答了自己的问题.如果您正在检测SHIFT键,则可以轻松区分大写和小写：

if(e.shiftKey){
   alert("You pressed a CAPITAL letter with the code " + e.keyCode);
}else{
   alert("You pressed a LOWERCASE letter with the code " + e.keyCode);
}

或者我误解了你的问题？

更新：通过添加32,可以轻松将大写ASCII代码转换为小写ASCII代码,因此您需要做的就是：

<html>
<head>
<title>Test</title>

<script type="text/javascript">

function showChar(e){
  if(e.keyCode!=16){ // If the pressed key is anything other than SHIFT
        if(e.keyCode >= 65 && e.keyCode <= 90){ // If the key is a letter
            if(e.shiftKey){ // If the SHIFT key is down, return the ASCII code for the capital letter
                alert("ASCII Code: "+e.keyCode);
            }else{ // If the SHIFT key is not down, convert to the ASCII code for the lowecase letter
                alert("ASCII Code: "+(e.keyCode+32));
            }
        }else{
            alert("ASCII Code (non-letter): "+e.keyCode);
        }
  }
}

</script>
</head>

<body onkeydown="showChar(event);">
<p>Press any character key, with or without holding down
 the SHIFT key.<br /></p>
</body>
</html>

更新2：试试这个：

<html>
<head>
<title>Test</title>

<script type="text/javascript">

function showChar(e){
  if(e.keyCode!=16){ // If the pressed key is anything other than SHIFT
        c = String.fromCharCode(e.keyCode);
        if(e.shiftKey){ // If the SHIFT key is down, return the ASCII code for the capital letter
            alert("ASCII Code: "+e.keyCode+" Character: "+c);
        }else{ // If the SHIFT key is not down, convert to the ASCII code for the lowecase letter
            c = c.toLowerCase(c);
            alert("ASCII Code: "+c.charCodeAt(0)+" Character: "+c);
        }
  }
}

</script>
</head>

<body onkeydown="showChar(event);">
<p>Press any character key, with or without holding down
 the SHIFT key.<br /></p>
</body>
</html>

标签：onkeydown,javascript
来源： https://codeday.me/bug/20191007/1869738.html