往textarea中光标所在位置插入文本

$(".addFullIn").click( function () {
$(".questionName").insertContent("( )");
});
//$(".addFullIn")为点击按钮
//$(".questionName")为要插入的文本框
//insertContent("( )")括号内为要插入的内容
(function ($) {
$.fn.extend({
insertContent: function (myValue, t) {
var $t = $(this)[0];
if (document.selection) { // ie
this.focus();
var sel = document.selection.createRange();
sel.text = myValue;
this.focus();
sel.moveStart('character', -l);
var wee = sel.text.length;
if (arguments.length == 2) {
var l = $t.value.length;
sel.moveEnd("character", wee + t);
t <= 0 ? sel.moveStart("character", wee - 2 * t
- myValue.length) : sel.moveStart(
"character", wee - t - myValue.length);
sel.select();
}
} else if ($t.selectionStart
|| $t.selectionStart == '0') {
var startPos = $t.selectionStart;
var endPos = $t.selectionEnd;
var scrollTop = $t.scrollTop;
$t.value = $t.value.substring(0, startPos)
+ myValue
+ $t.value.substring(endPos,
$t.value.length);
this.focus();
$t.selectionStart = startPos + myValue.length;
$t.selectionEnd = startPos + myValue.length;
$t.scrollTop = scrollTop;
if (arguments.length == 2) {
$t.setSelectionRange(startPos - t,
$t.selectionEnd + t);
this.focus();
}
} else {
this.value += myValue;
this.focus();
}
}
})
})(jQuery);