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();