转载别人的, 借鉴一下
<!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>JavaScript 获取/设置光标位置,兼容Input&&TextArea。</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<style>
body { margin: 32px; font-family: Verdana, sans-serif; font-size: 13px; }
.title { font-size: 18px; font-weight: bolder;margin:40px 0; }
.input { 50%; font-family: Verdana, sans-serif; font-size: 13px; text-indent: 2px; }
</style>
<script>
//获取光标位置
//单行文本框
function getPositionForInput(ctrl){
var CaretPos = 0;
if (document.selection) { // IE Support
ctrl.focus();
var Sel = document.selection.createRange();
Sel.moveStart('character', -ctrl.value.length);
CaretPos = Sel.text.length;
}else if(ctrl.selectionStart || ctrl.selectionStart == '0'){// Firefox support
CaretPos = ctrl.selectionStart;
}
return (CaretPos);
}
//多行文本框
function getPositionForTextArea(ctrl) {
var CaretPos = 0;
if(document.selection) {// IE Support
ctrl.focus();
var Sel = document.selection.createRange();
var Sel2 = Sel.duplicate();
Sel2.moveToElementText(ctrl);
var CaretPos = -1;
while(Sel2.inRange(Sel)){
Sel2.moveStart('character');
CaretPos++;
}
}else if(ctrl.selectionStart || ctrl.selectionStart == '0'){// Firefox support
CaretPos = ctrl.selectionStart;
}
return (CaretPos);
}
//设置光标位置函数
function setCursorPosition(ctrl, pos){
if(ctrl.setSelectionRange){
ctrl.focus();
ctrl.setSelectionRange(pos,pos);
}
else if (ctrl.createTextRange) {
var range = ctrl.createTextRange();
range.collapse(true);
range.moveEnd('character', pos);
range.moveStart('character', pos);
range.select();
}
}
//test
function process( id,targetId ){
var no = document.getElementById(id).value;
setCursorPosition(document.getElementById(targetId),no);
}
</script>
</head>
<body>
<div class="title">JavaScript 获取/设置光标位置,兼容Input&&TextArea：</div>
<div class="title">单行文本框</div>
<p><input class="input" id="textbox" name="textbox" value="Hi,www.jb51.net!!!" /></p>
<input type="button" onclick="alert( getPositionForInput( document.getElementById('textbox') ) )" value="Get Position">
输入位置: <input type="text" id="no1" size="1" /><input type="button" onclick="process('no1','textbox');" value="Set Position">
<div class="title">多行文本框</div>
<textarea id="zhangdanNum" name="zhangdanNum" style="height:66px;246px;overflow:hidden">Hi,CssRain!!!</textarea>
<input type="button" onclick="alert( getPositionForTextArea( document.getElementById('zhangdanNum') ) )" value="Get Position">
输入位置: <input type="text" id="no2" size="1" /><input type="button" onclick="process('no2','zhangdanNum');" value="Set Position">
</body>
</html>