无法将隐藏字段中的值复制到另一个HTML元素中？

Question

使用链接

https://demo.owncloud.org/index.php/apps/files/?dir=/&fileid=2

我想使用隐藏字段

HTML

<div id="controls" style="width: 1100px; min-width: 1100px;">
<div class="breadcrumb">
    <div class="crumb svg last" data-dir="/">
        <a href="/index.php/apps/files?dir=/">
            <img class="svg" src="/core/img/places/home.svg" alt="Home">
        </a>
    </div>
</div>

<div class="button view-switcher" id="gallery-button">
    <div id="button-loading"></div>
    <img alt="Gallery view" src="/core/img/actions/toggle-pictures.svg" class="svg">
</div>

<div class="actions creatable" style="">
    <a class="button new" href="#" data-original-title="" title="">
        <span class="icon icon-add"></span>
        <span class="hidden-visually">New</span>
    </a>
    <div id="uploadprogresswrapper">
        <div id="uploadprogressbar">
            <em style="display:none" class="label outer">
                <span class="desktop">Uploading...</span>
                <span class="mobile">...</span>
            </em>
        </div>
        <input type="button" value="" style="display:none" class="stop icon-close">
    </div>
</div>

<div id="file_action_panel" activeaction="false"></div>
<div class="notCreatable notPublic hidden">
    You don’t have permission to upload or create files here
</div>
<input type="hidden" id="permissions" value="31" name="permissions">
<input type="hidden" value="537919488" name="MAX_FILE_SIZE" id="max_upload">
<input type="hidden" value="537919488" id="upload_limit">
<input type="hidden" value="979339338" id="free_space">
<input type="hidden" value="(max )" class="max_human_file_size">

的Javascript

JS的相关部分如下所示，请查看

if (response.data !== undefined && response.data.uploadMaxFilesize !== undefined) {
                $('#max_upload').val(response.data.uploadMaxFilesize);
                $('#free_space').val(response.data.freeSpace);
                $('#upload.button').attr('data-original-title', response.data.maxHumanFilesize);
                $('#usedSpacePercent').val(response.data.usedSpacePercent);
                $('#owner').val(response.data.owner);
                $('#ownerDisplayName').val(response.data.ownerDisplayName);
                Files.displayStorageWarnings();

使用代码

显示

My name is <span id="free_space"></span> ...!!!

代码无效，我用firebug

尝试了

工作代码（尝试）

<script type="text/javascript">
 document.getElementById('dem0').value=document.getElementById("free_space").value
   </script>
  My name is <span id="dem0"></span> ...!!!

解决

<script type="text/javascript">
 var e=document.getElementById("free_space").value;
 document.getElementById("dem0").textContent=e;

   </script>