为什么此javascript网址验证程序失败？

Question

I have the following code to validate if a person entered a "valid" url in a textbox:

 function validateURL(textval) {
var urlregex = new RegExp(
    "^(http:\/\/www.|https:\/\/www.|ftp:\/\/www.|www.){1}([0-9A-Za-z]+\.)");
return urlregex.test(textval);

}

a user is getting an error where this is returning false for what seems like a valid urL

http://a.website.com/issues/i#browse/TEST-111

Can someone confirm why this example wouldn't pass the "valid url" test?

Answer 1

Can someone confirm why this example wouldn't pass the "valid url" test?

The main trouble with the regex is that www. part is obligatory in the pattern.

If you want to make it optional, use a ? modifier with a group around it ( (?:www\\.)? ):

^(?:(?:(?:ftp|https?):\/\/)?)(?:www\.)?[0-9A-Za-z]+(?:\.[0-9A-Za-z]+)*

This will match http://a.website.com part. To match the whole string, you can use:

^(?:(?:(?:ftp|https?):\/\/)?)(www\.)?[0-9A-Za-z]+(?:\.[0-9A-Za-z]+)*(?:\/[^\/]*)*$

See demo

 var re = /^(?:(?:(?:ftp|https?):\\/\\/)?)(www\\.)?[0-9A-Za-z]+(?:\\.[0-9A-Za-z]+)*(?:\\/[^\\/]*)*$/; var str = 'http://a.website.com/issues/i#browse/TEST-111'; if ((m = re.exec(str)) !== null) { document.getElementById("res").innerHTML = m[0]; } 

 <div id="res"/> 

Answer 2

Your regex requires that the host name portion starts with www. (this is not a requirement for URLs in general). The URL you are testing does not include www. .

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There are many other reasons why the regex is broken (you don't test past the first character after www. , your attempt to do so bans many characters that are allowed in URLs, etc) but that is why the URL you have isn't passing.