我试图显示在另一个文本区域中在一个文本区域中键入/粘贴/剪切/删除的内容。但是按退格键和删除键时出现问题。我可能也会遇到删除选择，剪切，粘贴，撤消，重做等问题。我怎样才能最好地解决这个问题？码：
<html>
<head>
<title>Live Text Sync</title>
<meta charset="utf-8"/>
</head>
<body>
<textarea id="a"></textarea>
<textarea id="b"></textarea>
<script>
var a = document.getElementById("a");
var b = document.getElementById("b");
a.onkeydown = function(e) {
if(!e.ctrlKey) {
if (e.which >= 65) {//A
var letter = String.fromCharCode(e.which);
if (!e.shiftKey) letter = letter.toLowerCase();
b.value = b.value.substring(0, a.selectionStart) + letter + b.value.substring(a.selectionEnd);
} else if (e.which === 8) {//backspace
var text = b.value;
var till = a.selectionStart === 0 ? 0 : a.selectionStart - 1;
b.value = text.substring(0, till) + text.substring(a.selectionEnd);
} else if (e.which === 46) {//delete
var text = b.value;
var van = text.length < a.selectionEnd ? a.selectionEnd : a.selectionEnd + 1;
b.value = text.substring(0, a.selectionStart) + text.substring(van);
}
}
}
</script>
</body>
</html>最佳答案
有什么理由不使用.value同步2个textarea吗？
<html>
<head>
<title>Live Text Sync</title>
<meta charset="utf-8" />
</head>
<body>
<textarea id="a"></textarea>
<textarea id="b"></textarea>
<script>
var a = document.getElementById("a");
var b = document.getElementById("b");
a.oninput = function(e) {
b.value = a.value;
}
</script>
</body>
</html>