验证网址并匹配空字符串的正则表达式? [英] A regex that validates a web address and matches an empty string?

问题描述

当前表达式验证网址 (HTTP)，如何更改它以便空字符串也匹配?

The current expression validates a web address (HTTP), how do I change it so that an empty string also matches?

(http|https):\/\/[\w\-_]+(\.[\w\-_]+)+([\w\-\.,@?^=%&:/~\+#]*[\w\-\@?^=%&/~\+#])?

推荐答案

如果您想修改表达式以匹配一个完全空的字符串或一个完整的 URL，您将需要使用锚元字符 ^ 和 $(分别匹配行的开头和结尾).

If you want to modify the expression to match either an entirely empty string or a full URL, you will need to use the anchor metacharacters ^ and $ (which match the beginning and end of a line respectively).

^(|https?:\/\/[\w\-_]+(\.[\w\-_]+)+([\w\-\.,@?^=%&:/~\+#]*[\w\-\@?^=%&/~\+#])?)$

正如直接指出的那样，您可以稍微简化一下协议的匹配，所以我也为您提供了.

As dirkgently pointed out, you can simplify your match for the protocol a little, so I've included that for you too.

不过，如果您在程序或脚本中使用此表达式，则使用语言自己的方法来检查输入是否为空可能更简单.

Though, if you are using this expression from within a program or script, it may be simpler for you to use the languages own means of checking if the input is empty.

// in no particular language...
if input.length > 0 then
    if input matches <regex> then
        input is a URL
    else
        input is invalid
else
    input is empty

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