如何检查给定的字符串是否是有效的URL地址?
我对正则表达式的知识是基本的，不允许我从我已经在网上看到的数百个正则表达式中进行选择。
当前回答
Javascript现在有一个名为new URL()的URL构造函数。它允许您完全跳过REGEX。
/** * * The URL() constructor returns a newly created URL object representing * the URL defined by the parameters. * * https://developer.mozilla.org/en-US/docs/Web/API/URL/URL * */ let requestUrl = new URL('https://username:password@developer.mozilla.org:8080/en-US/docs/search.html?par1=abc&par2=123&par3=true#Recent'); let urlParts = { origin: requestUrl.origin, href: requestUrl.href, protocol: requestUrl.protocol, username: requestUrl.username, password: requestUrl.password, host: requestUrl.host, hostname: requestUrl.hostname, port: requestUrl.port, pathname: requestUrl.pathname, search: requestUrl.search, searchParams: { par1: String(requestUrl.searchParams.get('par1')), par2: Number(requestUrl.searchParams.get('par2')), par3: Boolean(requestUrl.searchParams.get('par3')), }, hash: requestUrl.hash }; console.log(urlParts);
其他回答
Mathias Bynens有一篇关于大量正则表达式的最佳比较的很棒的文章:寻找完美的URL验证正则表达式
最好的一个帖子有点长，但它几乎可以匹配任何你可以扔给它的东西。
JavaScript版本
/^(?:(?:(?:https?|ftp):)?\/\/)(?:\S+(?::\S*)?@)?(?:(?!(?:10|127)(?:\.\d{1,3}){3})(?!(?:169\.254|192\.168)(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z0-9\u00a1-\uffff][a-z0-9\u00a1-\uffff_-]{0,62})?[a-z0-9\u00a1-\uffff]\.)+(?:[a-z\u00a1-\uffff]{2,}\.?))(?::\d{2,5})?(?:[/?#]\S*)?$/i
PHP版本(使用%符号作为分隔符)
%^(?:(?:(?:https?|ftp):)?\/\/)(?:\S+(?::\S*)?@)?(?:(?!(?:10|127)(?:\.\d{1,3}){3})(?!(?:169\.254|192\.168)(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z0-9\x{00a1}-\x{ffff}][a-z0-9\x{00a1}-\x{ffff}_-]{0,62})?[a-z0-9\x{00a1}-\x{ffff}]\.)+(?:[a-z\x{00a1}-\x{ffff}]{2,}\.?))(?::\d{2,5})?(?:[/?#]\S*)?$%iuS
就我所知，这个表达对我有好处-
(https?:\/\/(?:www\.|(?!www))[a-zA-Z0-9][a-zA-Z0-9-]+[a-zA-Z0-9]\.[^\s]{2,}|https?:\/\/(?:www\.|(?!www))[a-zA-Z0-9]\.[^\s]{2,}|www\.[a-zA-Z0-9]\.[^\s]{2,})
工作示例,
function RegExForUrlMatch() { var expression = /(https?:\/\/(?:www\.|(?!www))[a-zA-Z0-9][a-zA-Z0-9-]+[a-zA-Z0-9]\.[^\s]{2,}|https?:\/\/(?:www\.|(?!www))[a-zA-Z0-9]\.[^\s]{2,}|www\.[a-zA-Z0-9]\.[^\s]{2,})/g; var regex = new RegExp(expression); var t = document.getElementById("url").value; if (t.match(regex)) { document.getElementById("demo").innerHTML = "Successful match"; } else { document.getElementById("demo").innerHTML = "No match"; } } <input type="text" id="url" placeholder="url" onkeyup="RegExForUrlMatch()"> <p id="demo">Please enter a URL to test</p>
非验证uri引用解析器
为了便于参考，这里是IETF规范:(TXT | HTML)。特别地，附录b用正则表达式解析URI引用演示了如何解析有效的正则表达式。这被描述为，
这是一个非验证URI引用解析器的例子，它将接受任何给定的字符串并提取URI组件。
下面是它们提供的正则表达式:
^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?
正如其他人所说，最好将此留给您已经在使用的库/框架。
什么平台?如果使用。net，请使用System.Uri。TryCreate，不是正则表达式。
例如:
static bool IsValidUrl(string urlString)
{
Uri uri;
return Uri.TryCreate(urlString, UriKind.Absolute, out uri)
&& (uri.Scheme == Uri.UriSchemeHttp
|| uri.Scheme == Uri.UriSchemeHttps
|| uri.Scheme == Uri.UriSchemeFtp
|| uri.Scheme == Uri.UriSchemeMailto
/*...*/);
}
// In test fixture...
[Test]
void IsValidUrl_Test()
{
Assert.True(IsValidUrl("http://www.example.com"));
Assert.False(IsValidUrl("javascript:alert('xss')"));
Assert.False(IsValidUrl(""));
Assert.False(IsValidUrl(null));
}
(感谢@Yoshi提供javascript技巧:)
我一直在写一篇深入的文章，讨论使用正则表达式进行URI验证。它基于RFC3986。
正则表达式URI验证
虽然这篇文章还不完整，但我已经提出了一个PHP函数，它在验证HTTP和FTP url方面做得非常好。以下是当前版本:
// function url_valid($url) { Rev:20110423_2000
//
// Return associative array of valid URI components, or FALSE if $url is not
// RFC-3986 compliant. If the passed URL begins with: "www." or "ftp.", then
// "http://" or "ftp://" is prepended and the corrected full-url is stored in
// the return array with a key name "url". This value should be used by the caller.
//
// Return value: FALSE if $url is not valid, otherwise array of URI components:
// e.g.
// Given: "http://www.jmrware.com:80/articles?height=10&width=75#fragone"
// Array(
// [scheme] => http
// [authority] => www.jmrware.com:80
// [userinfo] =>
// [host] => www.jmrware.com
// [IP_literal] =>
// [IPV6address] =>
// [ls32] =>
// [IPvFuture] =>
// [IPv4address] =>
// [regname] => www.jmrware.com
// [port] => 80
// [path_abempty] => /articles
// [query] => height=10&width=75
// [fragment] => fragone
// [url] => http://www.jmrware.com:80/articles?height=10&width=75#fragone
// )
function url_valid($url) {
if (strpos($url, 'www.') === 0) $url = 'http://'. $url;
if (strpos($url, 'ftp.') === 0) $url = 'ftp://'. $url;
if (!preg_match('/# Valid absolute URI having a non-empty, valid DNS host.
^
(?P<scheme>[A-Za-z][A-Za-z0-9+\-.]*):\/\/
(?P<authority>
(?:(?P<userinfo>(?:[A-Za-z0-9\-._~!$&\'()*+,;=:]|%[0-9A-Fa-f]{2})*)@)?
(?P<host>
(?P<IP_literal>
\[
(?:
(?P<IPV6address>
(?: (?:[0-9A-Fa-f]{1,4}:){6}
| ::(?:[0-9A-Fa-f]{1,4}:){5}
| (?: [0-9A-Fa-f]{1,4})?::(?:[0-9A-Fa-f]{1,4}:){4}
| (?:(?:[0-9A-Fa-f]{1,4}:){0,1}[0-9A-Fa-f]{1,4})?::(?:[0-9A-Fa-f]{1,4}:){3}
| (?:(?:[0-9A-Fa-f]{1,4}:){0,2}[0-9A-Fa-f]{1,4})?::(?:[0-9A-Fa-f]{1,4}:){2}
| (?:(?:[0-9A-Fa-f]{1,4}:){0,3}[0-9A-Fa-f]{1,4})?:: [0-9A-Fa-f]{1,4}:
| (?:(?:[0-9A-Fa-f]{1,4}:){0,4}[0-9A-Fa-f]{1,4})?::
)
(?P<ls32>[0-9A-Fa-f]{1,4}:[0-9A-Fa-f]{1,4}
| (?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}
(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)
)
| (?:(?:[0-9A-Fa-f]{1,4}:){0,5}[0-9A-Fa-f]{1,4})?:: [0-9A-Fa-f]{1,4}
| (?:(?:[0-9A-Fa-f]{1,4}:){0,6}[0-9A-Fa-f]{1,4})?::
)
| (?P<IPvFuture>[Vv][0-9A-Fa-f]+\.[A-Za-z0-9\-._~!$&\'()*+,;=:]+)
)
\]
)
| (?P<IPv4address>(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}
(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))
| (?P<regname>(?:[A-Za-z0-9\-._~!$&\'()*+,;=]|%[0-9A-Fa-f]{2})+)
)
(?::(?P<port>[0-9]*))?
)
(?P<path_abempty>(?:\/(?:[A-Za-z0-9\-._~!$&\'()*+,;=:@]|%[0-9A-Fa-f]{2})*)*)
(?:\?(?P<query> (?:[A-Za-z0-9\-._~!$&\'()*+,;=:@\\/?]|%[0-9A-Fa-f]{2})*))?
(?:\#(?P<fragment> (?:[A-Za-z0-9\-._~!$&\'()*+,;=:@\\/?]|%[0-9A-Fa-f]{2})*))?
$
/mx', $url, $m)) return FALSE;
switch ($m['scheme']) {
case 'https':
case 'http':
if ($m['userinfo']) return FALSE; // HTTP scheme does not allow userinfo.
break;
case 'ftps':
case 'ftp':
break;
default:
return FALSE; // Unrecognized URI scheme. Default to FALSE.
}
// Validate host name conforms to DNS "dot-separated-parts".
if ($m['regname']) { // If host regname specified, check for DNS conformance.
if (!preg_match('/# HTTP DNS host name.
^ # Anchor to beginning of string.
(?!.{256}) # Overall host length is less than 256 chars.
(?: # Group dot separated host part alternatives.
[A-Za-z0-9]\. # Either a single alphanum followed by dot
| # or... part has more than one char (63 chars max).
[A-Za-z0-9] # Part first char is alphanum (no dash).
[A-Za-z0-9\-]{0,61} # Internal chars are alphanum plus dash.
[A-Za-z0-9] # Part last char is alphanum (no dash).
\. # Each part followed by literal dot.
)* # Zero or more parts before top level domain.
(?: # Explicitly specify top level domains.
com|edu|gov|int|mil|net|org|biz|
info|name|pro|aero|coop|museum|
asia|cat|jobs|mobi|tel|travel|
[A-Za-z]{2}) # Country codes are exactly two alpha chars.
\.? # Top level domain can end in a dot.
$ # Anchor to end of string.
/ix', $m['host'])) return FALSE;
}
$m['url'] = $url;
for ($i = 0; isset($m[$i]); ++$i) unset($m[$i]);
return $m; // return TRUE == array of useful named $matches plus the valid $url.
}
这个函数使用了两个正则表达式;一个用于匹配有效通用uri的子集(具有非空主机的绝对uri)，另一个用于验证DNS“点分隔部分”主机名。虽然这个函数目前只验证HTTP和FTP方案，但它的结构使它可以很容易地扩展以处理其他方案。
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