Question

<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资本 A 与小写 a ？以上算法触发相同的keyCode值。我需要在onkeydown按下时检测大写字母。

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。

Answer 1

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：大写ASCII代码可以通过添加32来轻松转换为小写ASCII代码，所以您需要做的就是：

<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>

Answer 2

更新，更清洁：使用event.key。没有更多的任意数字代码！

node.addEventListener('keydown', function(event) {
    const key = event.key; // "a", "1", "Shift", etc.
    if (/^[a-z]$/i.test(key)) { // or if (key.length === 1 && /[a-z]/i.test(key))
        const isCapital = event.shiftKey;
    }
});

Mozilla Docs

Supported Browsers

Answer 3

我在这个问题上做了很多搜索，因为我正在编写代码来限制输入元素（使用keyPress事件）仅限于字母字符。我使用的是“65到90之间的字符代码”，并且无法在字段中输入小写字母。

我终于发现JavaScript正在使用ASCII代码，所以我只添加了“和97到122之间”和中提琴！我可以输入大写和小写字母。即：

function alphaOnly(e) {
    'use strict';
    if (!e) { // compensates for IE's key code reporting.
        e = window.event;
    }
    var charCode = (e.which) ? e.which : event.keyCode;
    if ((charCode >= 65 && charCode <= 90) || (charCode >= 97 && charCode <= 122)) {
        return true;
    } else {
        return false;
    }
}

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

3 个答案: