$cache[$key] = empty($arr) ? NULL : $arr; return $cache[$key]; } // 门户 获取需要在频道显示的栏目主题数据 function portal_channel_thread($fid) { global $forumlist; if (empty($fid)) return NULL; $orderby = array('tid' => 1); $page = 1; // 遍历所有在频道显示内容的栏目 $category_forumlist = channel_category($fid); $arrlist = array(); $forum_tids = array(); $tidlist = array(); if ($category_forumlist) { foreach ($category_forumlist as &$_forum) { // 频道显示数据 $arrlist['list'][$_forum['fid']] = array( 'fid' => $_forum['fid'], 'name' => $_forum['name'], 'rank' => $_forum['rank'], 'type' => $_forum['type'], 'url' => $_forum['url'], 'channel_new' => $_forum['channel_new'], ); $forum_thread = thread_tid__find(array('fid' => $_forum['fid']), $orderby, $page, $_forum['channel_new'], 'tid', array('tid')); // 最新信息按栏目分组 foreach ($forum_thread as $key => $_thread) { $forum_tids[$key] = $_thread; } unset($forum_thread); } $tidlist += $forum_tids; } unset($category_forumlist); // 获取属性对应的tid集合 list($flaglist, $flagtids) = flag_thread_by_fid($fid); empty($flagtids) || $tidlist += $flagtids; unset($flagtids); // 频道置顶 $stickylist = sticky_list_thread($fid); empty($stickylist) || $tidlist += $stickylist; // 在这之前合并所有二维数组 tid值为键/array('tid值' => tid值) $tidarr = arrlist_values($tidlist, 'tid'); // 在这之前使用$tidarr = array_merge($tidarr, $arr)前合并所有一维数组 tid/array(1,2,3) if (empty($tidarr)) { $arrlist['list'] = isset($arrlist['list']) ? array_multisort_key($arrlist['list'], 'rank', FALSE, 'fid') : array(); return $arrlist; } $tidarr = array_unique($tidarr); $pagesize = count($tidarr); // 遍历获取的所有tid主题 $threadlist = well_thread_find_asc($tidarr, $pagesize); // 遍历时为升序，翻转为降序 $threadlist = array_reverse($threadlist); foreach ($threadlist as &$_thread) { // 各栏目最新内容 isset($forum_tids[$_thread['tid']]) AND $arrlist['list'][$_thread['fid']]['news'][$_thread['tid']] = $_thread; // 全站置顶内容 isset($stickylist[$_thread['tid']]) AND $arrlist['sticky'][$_thread['tid']] = $_thread; // 首页属性主题 if (!empty($flaglist)) { foreach ($flaglist as $key => $val) { if (isset($val['tids']) && in_array($_thread['tid'], $val['tids'])) { $arrlist['flaglist'][$key][array_search($_thread['tid'], $val['tids'])] = $_thread; ksort($arrlist['flaglist'][$key]); $arrlist['flag'][$_thread['tid']] = $_thread; } } } } unset($threadlist); if (isset($arrlist['sticky'])) { $i = 0; foreach ($arrlist['sticky'] as &$val) { ++$i; $val['i'] = $i; } } if (isset($arrlist['flag'])) { $i = 0; foreach ($arrlist['flag'] as &$val) { ++$i; $val['i'] = $i; } } if (isset($arrlist['flaglist'])) { foreach ($arrlist['flaglist'] as &$val) { $i = 0; foreach ($val as &$v) { ++$i; $v['i'] = $i; } } } isset($arrlist['list']) AND $arrlist['list'] = array_multisort_key($arrlist['list'], 'rank', FALSE, 'fid'); return $arrlist; } ?>javascript - IndexedDb - Check table exists and contains data - Stack Overflow

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    Using IndexedDB when my app first runs I populate it with some data, I want to ensure that when the database and tables are created that they do not already exists.

    Can I query the length of a table to see if it contains and data in JavaScript?

    Using IndexedDB when my app first runs I populate it with some data, I want to ensure that when the database and tables are created that they do not already exists.

    Can I query the length of a table to see if it contains and data in JavaScript?

    • javascript
    • html
    • indexeddb
    • jaydata
    Share Improve this question edited May 21, 2012 at 15:55 Peter Aron Zentai 11.7k6 gold badges42 silver badges72 bronze badges asked May 21, 2012 at 14:35 CLiownCLiown 13.8k50 gold badges127 silver badges205 bronze badges 1
    • CLiown, toske has the correct answer please accept it if it solves your case. – Deni Spasovski Commented Dec 5, 2013 at 20:04
    Add a comment  | 

    4 Answers 4

    Reset to default 8

    We can use the objectStoreNames property of IndexDB to check the existence of an ObjectStore.

    var db_object, object_store;
if( !db.objectStoreNames.contains(currentobjectstore) )
{
  db_object =  i_db.createObjectStore(currentobjectstore, {autoIncrement:true} );
 object_store = db.transaction(currentobjectstore, 'readwrite').objectStore(currentobjectstore);
} else {
 object_store = db.transaction(currentobjectstore, 'readwrite').objectStore(currentobjectstore);
}

    Best way is trying to open objectStore in try catch block. It is synchronous also. In case of an error you can create store for example:

    var store;
  try {
    store = request.transaction.objectStore('yourStore');
  }
  catch(e) {
    store = db.createObjectStore('yourStore');
}

    You can use objectStore.count() function, but i recommend storing some kind of meta-data that would say that your local db is initialized. Otherwise, you can have page-reload in middle of data creation and never have your data fully synced with remote data.

    The database is created if a database with the specified name does not exist else it opens it

    eg.var request = indexedDB.open("DataTbl");

    So if your db already exists it will just open it and about you checking if the contents in the table already exists then you can make an xyz objectstore and store some key/value flag pair inside it saying that the insertion was successful and check it later everytime when page is reloaded.

    Also you can give at try to count function specified by @toske

    ref :

    • http://www.ibm.com/developerworks/library/wa-indexeddb/

    • http://www.w3.org/TR/IndexedDB/

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