jQuery插件，将内容插入到光标处

(function ($) {
	$.fn.extend({
		insertAtCaret : function (myValue) {
			var $t = $(this)[0];
			if (document.selection) {
				this.focus();
				sel = document.selection.createRange();
				sel.text = myValue;
				this.focus();
			} else
				if ($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;
				} else {
					this.value += myValue;
					this.focus();
				}
		}
	})
})(jQuery);

//调用方法：$("select").insertAtCaret();