js代碼:在光標處添加字符串

<script type="text/javascript">
function insertAtCursor(myField, myValue) {
//IE support
if (document.selection) {
myField.focus();
sel = document.selection.createRange();
sel.text = myValue;
sel.select();
}
//MOZILLA/NETSCAPE support 
else if (myField.selectionStart || myField.selectionStart == '0') {
var startPos = myField.selectionStart;
var endPos = myField.selectionEnd;
// save scrollTop before insert www.keleyi.com
var restoreTop = myField.scrollTop;
myField.value = myField.value.substring(0, startPos) + myValue + myField.value.substring(endPos, myField.value.length);
if (restoreTop > 0) {
myField.scrollTop = restoreTop;
}
myField.focus();
myField.selectionStart = startPos + myValue.length;
myField.selectionEnd = startPos + myValue.length;
} else {
myField.value += myValue;
myField.focus();
}
} 
</script>
<form> 
<textarea id="demo" style="width:500px; height:300px">將鼠標定位到這裏的任意位置，然後點擊下面的按鈕，即可測試效果</textarea> 
<input type="button" οnclick=insertAtCursor(document.getElementById('demo'),'插入語句') value="插入" > 
</form>