<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Demo ： Textarea 元素的光标位置</title>
<style type="text/css">
#result
{
font-size: 18px;
line-height: 25px;
padding-left: 20px;
}
</style>
</head>
<body>
<div>
<h1>
Textarea 元素的光标位置</h1>
<ul>
<li>获取 Textarea 元素当前的光标位置</li>
<li>设置回原先的 Textarea 元素的光标位置</li>
<li>在 Textarea 元素的光标位置插入文本</li>
</ul>
<form action="#">
<textarea id="test" rows="8" cols="50"></textarea>
<p>
<input type="button" id="get" value="Get Cursor Position" />
<input type="button" id="set" value="Set Cursor Position" />
<input type="button" id="add" value="Add Text After Cursor Position" />
</p>
</form>
<h2>
Textarea Range：</h2>
<div id="result">
</div>
<script type="text/javascript">
document.getElementById("get").onclick = function () {
//alert(tx.value.length);
var tx = document.getElementById("test");
var re = document.getElementById("result");
var pos = cursorPosition.get(tx);
re.innerHTML = ("<strong>Range :</strong> (" + pos.start + ", " + pos.end + ")<br /><strong>Text :</strong> " + (!pos.text ? '//--' : pos.text));
}
document.getElementById("set").onclick = function () {
var tx = document.getElementById("test");
var re = document.getElementById("result");
var pos = cursorPosition.get(tx);
cursorPosition.set(tx, pos);
re.innerHTML = "";
}
document.getElementById("add").onclick = function () {
var tx = document.getElementById("test");
pos = cursorPosition.get(tx);
cursorPosition.add(tx, pos, input = prompt("你想插入替换的文本：", ""));
}
/**
* cursorPosition Object
*/
var cursorPosition = {
get: function (textarea) {
var rangeData = { text: "", start: 0, end: 0 };
if (textarea.setSelectionRange) { // W3C
textarea.focus();
rangeData.start = textarea.selectionStart;
rangeData.end = textarea.selectionEnd;
rangeData.text = (rangeData.start != rangeData.end) ? textarea.value.substring(rangeData.start, rangeData.end) : "";
} else if (document.selection) { // IE
textarea.focus();
var i,
oS = document.selection.createRange(),
// Don't: oR = textarea.createTextRange()
oR = document.body.createTextRange();
oR.moveToElementText(textarea);
rangeData.text = oS.text;
rangeData.bookmark = oS.getBookmark();
// object.moveStart(sUnit [, iCount])
// Return Value: Integer that returns the number of units moved.
for (i = 0; oR.compareEndPoints('StartToStart', oS) < 0 && oS.moveStart("character", -1) !== 0; i++) {
// Why? You can alert(textarea.value.length)
if (textarea.value.charAt(i) == '\r') {
i++;
}
}
rangeData.start = i;
rangeData.end = rangeData.text.length + rangeData.start;
}
return rangeData;
},
set: function (textarea, rangeData) {
var oR, start, end;
if (!rangeData) {
alert("You must get cursor position first.")
}
textarea.focus();
if (textarea.setSelectionRange) { // W3C
textarea.setSelectionRange(rangeData.start, rangeData.end);
} else if (textarea.createTextRange) { // IE
oR = textarea.createTextRange();
// Fixbug : ues moveToBookmark()
// In IE, if cursor position at the end of textarea, the set function don't work
if (textarea.value.length === rangeData.start) {
//alert('hello')
oR.collapse(false);
oR.select();
} else {
oR.moveToBookmark(rangeData.bookmark);
oR.select();
}
}
},
add: function (textarea, rangeData, text) {
var oValue, nValue, oR, sR, nStart, nEnd, st;
this.set(textarea, rangeData);
if (textarea.setSelectionRange) { // W3C
oValue = textarea.value;
nValue = oValue.substring(0, rangeData.start) + text + oValue.substring(rangeData.end);
nStart = nEnd = rangeData.start + text.length;
st = textarea.scrollTop;
textarea.value = nValue;
// Fixbug:
// After textarea.values = nValue, scrollTop value to 0
if (textarea.scrollTop != st) {
textarea.scrollTop = st;
}
textarea.setSelectionRange(nStart, nEnd);
} else if (textarea.createTextRange) { // IE
sR = document.selection.createRange();
sR.text = text;
sR.setEndPoint('StartToEnd', sR);
sR.select();
}
}
}
</script>
</div>
</body>
</html>