function insertHTMLToEditor(obj) 
{ 
   var oEditor = FCKeditorAPI.GetInstance("content"); 
   if(oEditor.EditMode == FCK_EDITMODE_WYSIWYG) 
   { 
       oEditor.InsertHtml(obj) 
   } 
   else 
   { 
       return false; 
   } 
} 

<script type = "text/javascript" >
//"添加/删除复选框"点击时如果按钮选中则添加"{#book#}"字符串到FCK内容里，反之删除字符串
//lineBook为FCK的ID号
function chk_but() {
  if (window.FCKeditorAPI !== undefined && FCKeditorAPI.GetInstance('txtContent') !== undefined) {
    if (document.getElementById('lineBook').checked) {
      FCKeditorAPI.GetInstance('txtContent').EditorDocument.body.innerHTML += "{#book#}";
    } else {
      FCKeditorAPI.GetInstance('txtContent').EditorDocument.body.innerHTML = FCKeditorAPI.GetInstance('txtContent').EditorDocument.body.innerHTML.replace("{#book#}", "");
    }
  }
} //end function chk_lineBook()
//内容里如果有{#book#}则选中"添加/删除复选框"
if (document.getElementById('txtContent').value.indexOf('{#book#}') >= 0 
  && window.FCKeditorAPI !== undefined 
  && FCKeditorAPI.GetInstance('txtContent') !== undefined) {
  document.getElementById('lineBook').checked = true;
} 
</script>

//向编辑器插入指定代码 
function insertHTMLToEditor(codeStr){ 
 var oEditor = FCKeditorAPI.GetInstance("content");
 oEditor.InsertHtml(codeStr); // "html"为HTML文本
}
//获取编辑器中HTML内容
function getEditorHTMLContents() {
 var oEditor = FCKeditorAPI.GetInstance("content");
 return(oEditor.GetXHTML(false));
}
// 获取编辑器中文字内容
function getEditorTextContents() {
 var oEditor = FCKeditorAPI.GetInstance("content");
 return(oEditor.EditorDocument.body.innerText);
}
// 设置编辑器中内容
function SetEditorContents(ContentStr) {
 var oEditor = FCKeditorAPI.GetInstance("content") ;
 oEditor.SetHTML(ContentStr) ;
}
//向编辑器插入指定代码 
function  insertHTMLToEditor(codeStr){ 
    var  oEditor  =  FCKeditorAPI.GetInstance( "content "); 
    if  (oEditor.EditMode==FCK_EDITMODE_WYSIWYG){ 
       oEditor.InsertHtml(codeStr); 
    }else{ 
       return  false; 
    } 
} 
//统计编辑器中内容的字数 
function  getLength(){ 
    var  oEditor  =  FCKeditorAPI.GetInstance( "content "); 
    var  oDOM  =  oEditor.EditorDocument; 
    var  iLength  ; 
    if(document.all){ 
       iLength  =  oDOM.body.innerText.length; 
    }else{ 
       var  r  =  oDOM.createRange(); 
       r.selectNodeContents(oDOM.body); 
       iLength  =  r.toString().length; 
    } 
    alert(iLength); 
} 
//执行指定动作 
function  ExecuteCommand(commandName){ 
    var  oEditor  =  FCKeditorAPI.GetInstance( "content ")  ; 
    oEditor.Commands.GetCommand(commandName).Execute()  ; 
}