$.fn.extend({    insertAtCursor : 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();        }    }});

    
     
      插入文本
      
           function insertExp() {        $("#content").insertAtCursor("测试插入文本");    }