在JavaScript正则表达式中使用前瞻匹配可选组

Question

我正在尝试用正则表达式解决字符串匹配问题.我需要匹配此表单的网址:

http://soundcloud.com/okapi23/dont-turn-your-back/

我需要"拒绝"此表单的网址:

http://soundcloud.com/okapi23/sets/happily-reversed/

尾随'/'显然是可选的.

所以基本上:

• 在主机名之后,可以有2或3个组,如果在第二个组中等于 "sets",则正则表达式不应该匹配.
• "sets"可以包含在URL中的任何其他位置
• "集合"需要完全匹配

到目前为止我提出的是http(s)?://(www\.)?soundcloud\.com/.+/(?!sets)\b(/.+)?失败的.

有什么建议？是否有任何库可以简化任务(例如,使尾部斜杠可选)？

Answer 1

假设OP想要测试以查看给定字符串是否包含满足以下要求的URL:

• URL方案必须是http:或https:.
• URL权限必须是//soundcloud.com或//www.soundcloud.com.
• URL路径必须存在,并且必须包含2或3个路径段.
• 第二个路径段不能是:"sets".
• 每个路径段必须包含一个或多个仅由字母数字字符组成的"单词"([A-Za-z0-9]),并且多个单词由一个短划线或下划线分隔.
• URL必须没有查询或片段组件.
• URL路径可以以可选的方式结束"/".
• URL应该不区分大小写.

这是一个经过测试的JavaScript函数(带有完全注释的正则表达式),可以解决这个问题:

function isValidCustomUrl(text) {
    /* Here is the regex commented in free-spacing mode:
    # Match specific URL having non-"sets" 2nd path segment.
    ^                          # Anchor to start of string.
    https?:                    # URL Scheme (http or https).
    //                         # Begin URL Authority.
    (?:www\.)?                 # Optional www subdomain.
    soundcloud\.com            # URL DNS domain.
    /                          # 1st path segment (can be: "sets").
    [A-Za-z0-9]+               # 1st word-portion (required).
    (?:                        # Zero or more extra word portions.
      [-_]                     # only if separated by one - or _.
      [A-Za-z0-9]+             # Additional word-portion.
    )*                         # Zero or more extra word portions.
    (?!/sets(?:/|$))           # Assert 2nd segment not "sets".
    (?:                        # 2nd and 3rd path segments.
      /                        # Additional path segment.
      [A-Za-z0-9]+             # 1st word-portion.
      (?:                      # Zero or more extra word portions.
        [-_]                   # only if separated by one - or _.
        [A-Za-z0-9]+           # Additional word-portion.
      )*                       # Zero or more extra word portions.
    ){1,2}                     # 2nd path segment required, 3rd optional.
    /?                         # URL may end with optional /.
    $                          # Anchor to end of string.
    */
    // Same regex in javascript syntax:
    var re = /^https?:\/\/(?:www\.)?soundcloud\.com\/[A-Za-z0-9]+(?:[-_][A-Za-z0-9]+)*(?!\/sets(?:\/|$))(?:\/[A-Za-z0-9]+(?:[-_][A-Za-z0-9]+)*){1,2}\/?$/i;
    if (re.test(text)) return true;
    return false;
}