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 - Error using both lookahead and look behind regex - Stack Overflow

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    javascript - Error using both lookahead and look behind regex - Stack Overflow

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    I am having a problem using the following regex. It works fine in regexr and rubular but it gives me an error when running it on node.js. I am fairly new to using regex and i'm not sure what i'm doing wrong. It will work if I knock off the (?<= ) so I presume that is the problem.

    I'm trying to match 'is' with a leading and trailing space using /(?<= )is(?= )|==/g

    Example with test words:

    Node error output 

     temp = temp.replace(/(?<= )is(?= )|==/g, '===');
^
SyntaxError: Invalid regular expression: /(?<= )is(?= )|==/: Invalid group
at new RegExp (unknown source)

    I am having a problem using the following regex. It works fine in regexr and rubular but it gives me an error when running it on node.js. I am fairly new to using regex and i'm not sure what i'm doing wrong. It will work if I knock off the (?<= ) so I presume that is the problem.

    I'm trying to match 'is' with a leading and trailing space using /(?<= )is(?= )|==/g

    Example with test words:
    http://regexr.?33781

    Node error output 

     temp = temp.replace(/(?<= )is(?= )|==/g, '===');
^
SyntaxError: Invalid regular expression: /(?<= )is(?= )|==/: Invalid group
at new RegExp (unknown source)
    • javascript
    • regex
    • node.js
    Share Improve this question edited Dec 21, 2012 at 16:34 FThompson 28.7k13 gold badges62 silver badges95 bronze badges asked Dec 21, 2012 at 16:32 SkinnyG33kSkinnyG33k 1,7314 gold badges24 silver badges30 bronze badges 0
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    2 Answers 2

    Reset to default 16

    JavaScript regex does not support lookbehind at all.

    Sources:

    • http://www.regular-expressions.info/lookaround.html#limitbehindand
    • http://www.regular-expressions.info/javascript.html
    • https://developer.mozilla/en-US/docs/JavaScript/Guide/Regular_Expressions

    However, you can fake it in some cases.

    Quite simply, this is because JavaScript regular expressions have no support for lookbehinds:

    http://www.regular-expressions.info/javascript.html

    Lookbehind is not supported at all. Lookahead is fully supported.

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