如何获取返回空节点集的跨度内容？

Question

这是我要提取信息的网站 div：

 <div class="_24er">
 <table class="_4dmd _4eok uiGrid _51mz" cols="4" cellspacing="0" cellpadding="0"><tbody>
    <tr class="_51mx">
    <td class="_5px7 _51m-">
    <span class="_5x8v _5a5j _5a5i">
    <span class="_5a4-">FÉV</span>
    <span class="_5a4z">11</span>
    </span>
    </td>
    <td class="_4dmi _51m-"><div class="_4dmj">
    <div class="_4dmk">
    <a data-hovercard="/ajax/hovercard/event.php?id=769853670060959" href="/events/769853670060959/?acontext=%7B%22source%22%3A5%2C%22action_history%22%3A[%7B%22surface%22%3A%22page%22%2C%22mechanism%22%3A%22main_list%22%2C%22extra_data%22%3A%22%5C%22[]%5C%22%22%7D]%2C%22has_source%22%3Atrue%7D" id="js_9a" aria-describedby="u_2r_1" aria-owns="">
    <span class=" _50f7"> HipHop Night With YOUSTAAZ (-60% Countdown Sur Toute La Carte) 
    </span>
    </a>
    </div>
    <div class="_4dml fsm fwn fcg">
    <span class="">11 févr. - 12 févr.</span>
    <span aria-hidden="true"> · </span>
    15 invités</div>
    </div>
    </td>
    <td class="_5pxd _51m-">
    <div class="_4dmn">
    <div class="_30n-">
    <a data-hovercard="/ajax/hovercard/hovercard.php?id=1276481845698447" href="https://xxxxxxx">JOBI - Gammarth</a>
    </div>
    <div class="_30n_">Tunis, Tunisie</div>
    </div></td>
    <td class="_4dmt _51mw _51m-">
    <div class="_4dmu">
    <div class="_2ib5">
    <div class="_2ib4">
    <div><button class="_4jy0 _4jy3 _517h _51sy _42ft" type="submit" value="1"><i alt="" class="_3-8_ img sp_7RV3BBvGAaI sx_1551de"></i>Ça m’intéresse</button></div>
    </div>
    </div>
    </div>
    </td>
    </tr>
    </tbody>
    </table>
    </div>

我正在尝试提取 span 节点的内容，如下所示：

<span class=" _50f7"> HipHop Night With YOUSTAAZ (-60% Countdown Sur Toute La Carte) 
</span>

我已经提取了日期节点（事件的月份和日期），但是当提取上面显示的跨度中的事件名称时，我得到空节点：

cc<-remDr$findElement(using = "css", "[class = '_24er']")
cc<-remDr$getPageSource()

page_events<-read_html(cc[[1]][1])

events =html_nodes(page_events,'._24er')

mois_data=html_nodes(page_events,'._24er > table > tbody > tr > td > span > ._5a4-')
jours_data=html_nodes(page_events,'._24er > table > tbody > tr > td > span > ._5a4z')
links_events_data=html_nodes(page_events,'._24er > table > tbody > tr > td > div> div > a ')

//getting the name of events : I get {xml_nodeset (0)} as a result
    nom_events_data=html_nodes(page_events,'._24er > table > tbody > tr > td > div> div > a > span > ._50f7')

//我试图使用 class 来获取内容，我得到这个错误：

Error in xml2::xml_text(x, trim = trim) : 
  object 'noms_events_data' not found

nom_events_data=html_nodes(page_events,"[class='._50f7']")

//我尝试使用 xpath ，与 xpath 相同的错误：

nom_events_data=html_nodes(page_events,xpath = '//*[@id="js_9a"]/span')

//结果总是字符(0)

noms_events = html_text(noms_events_data)

Answer 1

经文档验证，正确的语法是：

noms_events_data=html_nodes(page_events,"._50f7")

而不是：

noms_events_data=html_nodes(page_events,'[class="._50f7"]')

如何获取返回空节点集的跨度内容？

How to get the content of a span returning empty nodeset?

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