I would like to find out and keep track of the 'line number' (rows) of the cursor in a textarea. (The 'bigger picture' is to parse the text on the line every time a new line is created/modified/selected, if of course the text was not pasted in. This saves parsing the whole text un-necessarily at set intervals.)
There are a couple of posts on StackOverflow however none of them specifically answer my question, most questions are for cursor position in pixels or displaying lines numbers besides the textarea.
My attempt is below, it works fine when starting at line 1 and not leaving the textarea. It fails when clicking out of the textarea and back onto it on a different line. It also fails when pasting text into it because the starting line is not 1.
My JavaScript knowledge is pretty limited.
<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>
You would want to use selectionStart to do this.
<textarea onkeyup="getLineNumber(this, document.getElementById('lineNo'));" onmouseup="this.onkeyup();"></textarea>
<div id="lineNo"></div>
<script>
function getLineNumber(textarea, indicator) {
indicator.innerHTML = textarea.value.substr(0, textarea.selectionStart).split("\n").length;
}
</script>
This works when you change the cursor position using the mouse as well.
This is tough because of word wrap. It's a very easy thing to count the number of line breaks present, but what happens when the new row is because of word wrap? To solve this problem, it's useful to create a mirror (credit: github.com/jevin). Here's the idea:
- Create a mirror of the textarea
- Send the content from the beginning of the textarea to the cursor to the mirror
- Use the height of the mirror to extract the current row
jQuery.fn.trackRows = function() {
return this.each(function() {
var ininitalHeight, currentRow, firstIteration = true;
var createMirror = function(textarea) {
jQuery(textarea).after('<div class="autogrow-textarea-mirror"></div>');
return jQuery(textarea).next('.autogrow-textarea-mirror')[0];
}
var sendContentToMirror = function (textarea) {
mirror.innerHTML = String(textarea.value.substring(0,textarea.selectionStart-1)).replace(/&/g, '&').replace(/"/g, '"').replace(/'/g, ''').replace(/</g, '<').replace(/>/g, '>').replace(/\n/g, '<br />') + '.<br/>.';
calculateRowNumber();
}
var growTextarea = function () {
sendContentToMirror(this);
}
var calculateRowNumber = function () {
if(firstIteration){
ininitalHeight = $(mirror).height();
currentHeight = ininitalHeight;
firstIteration = false;
} else {
currentHeight = $(mirror).height();
}
// Assume that textarea.rows = 2 initially
currentRow = currentHeight/(ininitalHeight/2) - 1;
//remove tracker in production
$('.tracker').html('Current row: ' + currentRow);
}
// Create a mirror
var mirror = createMirror(this);
// Style the mirror
mirror.style.display = 'none';
mirror.style.wordWrap = 'break-word';
mirror.style.whiteSpace = 'normal';
mirror.style.padding = jQuery(this).css('padding');
mirror.style.width = jQuery(this).css('width');
mirror.style.fontFamily = jQuery(this).css('font-family');
mirror.style.fontSize = jQuery(this).css('font-size');
mirror.style.lineHeight = jQuery(this).css('line-height');
// Style the textarea
this.style.overflow = "hidden";
this.style.minHeight = this.rows+"em";
var ininitalHeight = $(mirror).height();
// Bind the textarea's event
this.onkeyup = growTextarea;
// Fire the event for text already present
// sendContentToMirror(this);
});
};
$(function(){
$('textarea').trackRows();
});
The two comments by Jakub P. May and Andrew Li Sep; indicate that the two individuals do not understand the nature of a row in a textarea.
The wrapping of text in a textarea is for the benefit of being able to read the text without the need to side scroll. The visual wrapping of the text to a visual new row, does not equal a new row.
This is the same basic and expected functionality that exists in all text editors including Notepad++, Notepad as well as Microsoft Word and the majority of text editing software.
Having a textarea or text editor input a hard line break when the text wraps would make it difficult to determine when a line starts and ends from a coding point of view. It would cause sentences to be broken up in the middle rather than the end and that would make it difficult to find that specific sentence in a text search as the line break would constitute an additional character in the sentence thereby causing the expected match to fail.
A soft line break, is not a line break, therefore the text, despite it's visual appearance, remains on the same row as it should be.
来源：https://stackoverflow.com/questions/9185630/find-out-the-line-row-number-of-the-cursor-in-a-textarea