我想找出并跟踪文本区域中光标的“行号”（行）。（“大图”是在每次创建/修改/选择新行时解析行上的文本，当然，如果文本没有粘贴进去。这可以节省不必要地以设置的间隔解析整个文本。）
StackOverflow 上有几篇文章，但没有一个专门回答我的问题，大多数问题都是关于光标位置（以像素为单位）或显示除 textarea 之外的行数。
我的尝试如下，从第 1 行开始并且不离开 textarea 时它工作正常。单击 textarea 并返回到另一行时失败。将文本粘贴到其中时也会失败，因为起始行不是 1。
我的 JavaScript 知识非常有限。
<html>
<head>
<title>DEVBug</title>
<script type="text/javascript">
var total_lines = 1; // total lines
var current_line = 1; // current line
var old_line_count;
// main editor function
function code(e) {
// declare some needed vars
var keypress_code = e.keyCode; // key press
var editor = document.getElementById('editor'); // the editor textarea
var source_code = editor.value; // contents of the editor
// work out how many lines we have used in total
var lines = source_code.split("\n");
var total_lines = lines.length;
// do stuff on key presses
if (keypress_code == '13') { // Enter
current_line += 1;
} else if (keypress_code == '8') { // Backspace
if (old_line_count > total_lines) { current_line -= 1; }
} else if (keypress_code == '38') { // Up
if (total_lines > 1 && current_line > 1) { current_line -= 1; }
} else if (keypress_code == '40') { // Down
if (total_lines > 1 && current_line < total_lines) { current_line += 1; }
} else {
//document.getElementById('keycodes').innerHTML += keypress_code;
}
// for some reason chrome doesn't enter a newline char on enter
// you have to press enter and then an additional key for \n to appear
// making the total_lines counter lag.
if (total_lines < current_line) { total_lines += 1 };
// putput the data
document.getElementById('total_lines').innerHTML = "Total lines: " + total_lines;
document.getElementById('current_line').innerHTML = "Current line: " + current_line;
// save the old line count for comparison on next run
old_line_count = total_lines;
}
</script>
</head>
<body>
<textarea id="editor" rows="30" cols="100" value="" onkeydown="code(event)"></textarea>
<div id="total_lines"></div>
<div id="current_line"></div>
</body>
</html>