te')); return $arr; } /* 遍历用户所有主题 * @param $uid 用户ID * @param int $page 页数 * @param int $pagesize 每页记录条数 * @param bool $desc 排序方式 TRUE降序 FALSE升序 * @param string $key 返回的数组用那一列的值作为 key * @param array $col 查询哪些列 */ function thread_tid_find_by_uid($uid, $page = 1, $pagesize = 1000, $desc = TRUE, $key = 'tid', $col = array()) { if (empty($uid)) return array(); $orderby = TRUE == $desc ? -1 : 1; $arr = thread_tid__find($cond = array('uid' => $uid), array('tid' => $orderby), $page, $pagesize, $key, $col); return $arr; } // 遍历栏目下tid 支持数组 $fid = array(1,2,3) function thread_tid_find_by_fid($fid, $page = 1, $pagesize = 1000, $desc = TRUE) { if (empty($fid)) return array(); $orderby = TRUE == $desc ? -1 : 1; $arr = thread_tid__find($cond = array('fid' => $fid), array('tid' => $orderby), $page, $pagesize, 'tid', array('tid', 'verify_date')); return $arr; } function thread_tid_delete($tid) { if (empty($tid)) return FALSE; $r = thread_tid__delete(array('tid' => $tid)); return $r; } function thread_tid_count() { $n = thread_tid__count(); return $n; } // 统计用户主题数 大数量下严谨使用非主键统计 function thread_uid_count($uid) { $n = thread_tid__count(array('uid' => $uid)); return $n; } // 统计栏目主题数 大数量下严谨使用非主键统计 function thread_fid_count($fid) { $n = thread_tid__count(array('fid' => $fid)); return $n; } ?>Javascript document.getElementById doesn't seem to work - Stack Overflow

科技改变生活-雨落星辰 - 所有的伟大,都源于一个勇敢的开始

    最新消息：雨落星辰是一个专注网站SEO优化、网站SEO诊断、搜索引擎研究、网络营销推广、网站策划运营及站长类的自媒体原创博客
    你的位置： 首页>programmer>Javascript document.getElementById doesn't seem to work - Stack Overflow

    Javascript document.getElementById doesn't seem to work - Stack Overflow

    programmeradmin3浏览0评论

    I have the following code, and the javascript console in chrome says "Can't read innerHTML property of null. Why does document.getElementById('display') turn up empty handed?

    <!DOCTYPE html>
<html>
    <head>
        <title>Chat 3</title>
        <script type="text/javascript">
            function showmsg(str){
                var display = document.getElementById('display');
                display.innerHTML += "<p>" + str + "</p>";
            }

            if("WebSockets" in window){
                pass;
            }else{
                showmsg("Your browser doesn't support WebSockets. Try Google Chrome.");
            }
        </script>

        <style type="text/css">
        #username { 
            padding: 0px;
            margin: 0px;
            height: 26px;
            width: 400px;
        }

        /* ADDED container div that wraps onlineusers and display */
        #container {
          margin: 10px 0;
        }

        /* use float: left to put them side-by-side */
        #display { 
            padding: 0px;
            margin: 0px;
            border-style: solid;
            border-width: 1px;
            overflow: auto;
            height: 400px;
            width: 400px;
            float: left;
        }

        #onlineusers { 
            padding: 0px;
            margin: 0px;
            height: 400px;
            width: 200px;
            border-style: solid;
            border-width: 1px;
            float: left;
        }

        /* Added container2 to wrap inputline and sendbutton */
        #container2 {
            margin: 10px 0;
        }

        #inputline { 
            padding: 0px;
            margin: 0px;
            height: 26px;
            width: 350px;
            float: left;
        }

        #sendbutton {
            padding: 0px;
            margin: 0px;
            height: 30px;
            width: 50px;
            float: left;
        }

        /* this is a well used "hack". */
        .clearfix {
          clear: both;
        }
        </style>
    </head>
    <body onload="document.getElementById("username").focus()">
            <input type="text" id="username" />
            <div id="container">
                <div id="display"></div>
                <div id="onlineusers"></div>
                <div class="clearfix"></div>
            </div>

            <div id="container2">
                <input type="text" id="inputline" length="55" />
                <input type="button" id="sendbutton" value="Send" />
            </div>
    </body>
</html>

    I have the following code, and the javascript console in chrome says "Can't read innerHTML property of null. Why does document.getElementById('display') turn up empty handed?

    <!DOCTYPE html>
<html>
    <head>
        <title>Chat 3</title>
        <script type="text/javascript">
            function showmsg(str){
                var display = document.getElementById('display');
                display.innerHTML += "<p>" + str + "</p>";
            }

            if("WebSockets" in window){
                pass;
            }else{
                showmsg("Your browser doesn't support WebSockets. Try Google Chrome.");
            }
        </script>

        <style type="text/css">
        #username { 
            padding: 0px;
            margin: 0px;
            height: 26px;
            width: 400px;
        }

        /* ADDED container div that wraps onlineusers and display */
        #container {
          margin: 10px 0;
        }

        /* use float: left to put them side-by-side */
        #display { 
            padding: 0px;
            margin: 0px;
            border-style: solid;
            border-width: 1px;
            overflow: auto;
            height: 400px;
            width: 400px;
            float: left;
        }

        #onlineusers { 
            padding: 0px;
            margin: 0px;
            height: 400px;
            width: 200px;
            border-style: solid;
            border-width: 1px;
            float: left;
        }

        /* Added container2 to wrap inputline and sendbutton */
        #container2 {
            margin: 10px 0;
        }

        #inputline { 
            padding: 0px;
            margin: 0px;
            height: 26px;
            width: 350px;
            float: left;
        }

        #sendbutton {
            padding: 0px;
            margin: 0px;
            height: 30px;
            width: 50px;
            float: left;
        }

        /* this is a well used "hack". */
        .clearfix {
          clear: both;
        }
        </style>
    </head>
    <body onload="document.getElementById("username").focus()">
            <input type="text" id="username" />
            <div id="container">
                <div id="display"></div>
                <div id="onlineusers"></div>
                <div class="clearfix"></div>
            </div>

            <div id="container2">
                <input type="text" id="inputline" length="55" />
                <input type="button" id="sendbutton" value="Send" />
            </div>
    </body>
</html>
    • javascript
    • getelementbyid
    Share Improve this question asked Jul 9, 2010 at 5:33 lowerkeylowerkey 8,33518 gold badges70 silver badges102 bronze badges
    Add a ment  | 

    3 Answers 3

    Reset to default 7

    Move your script-section down to the bottom of the page. Otherwise it is executed before the page has been loaded.

    Btw: Putting scripts at the bottom of your page is even a "best practice" and remended by Google, Yahoo & Co

    You're calling showmsg before the whole page (and hence the display div) is loaded. Hence the error. Call it from onload and it'll work.

    Add this function to the <head>

    function handleLoad()
{
  document.getElementById("username").focus()
  if("WebSockets" in window){
   pass;
  }else{
    showmsg("Your browser doesn't support WebSockets. Try Google Chrome.");
  }
}

    and call it from onload

    <body onload="handleLoad()">

    Put your script tag at the end of the document:. In your case the page has not been pletely parsed into DOM tree, but your script executes anyway:

           <body onload="document.getElementById('username').focus()">
           <input type="text" id="username" />
           <div id="container">
               <div id="display"></div>
               <div id="onlineusers"></div>
               <div class="clearfix"></div>
           </div>

           <div id="container2">
               <input type="text" id="inputline" length="55" />
               <input type="button" id="sendbutton" value="Send" />
           </div>

           <script type="text/javascript">
           function showmsg(str){
               var display = document.getElementById('display');
               display.innerHTML += "<p>" + str + "</p>";
           }

           if("WebSockets" in window){
              pass;
           }else{
               showmsg("Your browser doesn't support WebSockets. Try Google Chrome.");
           }
       </script>
   </body>

    This is also considered a good practice for performance reasons: http://developer.yahoo./performance/rules.html#js_bottom

    与本文相关的文章

    发布评论

    评论列表(0)

    1. 暂无评论