排除正则表达式中的网址格式

Question

This is my input string

<div>http://google.com</div><span data-user-info="{\\"name\\":\\"subash\\", \\"url\\" : \\"http://userinfo.com?userid=33\\"}"></span><a href="https://contact.me"></a>http://byebye.com is a dummy website.

for this case I need to match only first and last occurrence of http. because those are innerText in html point of view. http in attribute values we need to ignore. I build following regex.

(?<!href=\"|src=\"|value=\"|href=\'|src=\'|value=\'|=)(http://|https://|ftp://|sftp://)

It is working fine for first and last occurrence. but this is also matching the second occurrence of http. the link(http) in the attribute we don't need to match.

FYI : I am trying negative lookahead, but that is seems not helping. This is the one with negative lookahead.

(?<!href=\"|src=\"|value=\"|href=\'|src=\'|value=\'|=)(http://|https://|ftp://|sftp://).*?(?!>)

Answer 1

Update after having more details

Another approach is to take benefit from regex's "greediness". /(http).*(http)/g will match as much text as possible from the first to the last occurrence of "http". Below example illustrates this behavior. (http) are capturing groups - replace those with your full regex. I simplified the regex for easier understanding.

var text ='<div>http://google.com</div><span data-user-info="{\"name\":\"subash\", \"url\" : \"http://userinfo.com?userid=33\"}"></span><a href="https://contact.me"></a>http://byebye.com is a dummy website.'
var regex = /(http).*(http)/g;
var match = regex.exec(text);
//match[0] is entire matched text
var firstMatch = match[1]; // = "http"
var lastMatch = match[2]; // = "http"

This example is specific of JavaScript, but Java regexps (and many other regex engines) work the same way. (http).*(http) would work too.

---

Do you aim to match the first and the last line or the first and the last occurrence of a string?

If the former is correct, I would split the text into lines first, and then regex-match the first and the last line.

//Split into lines:
var lines = yourMultiLineText.split(/[\r\n]+/g);

If the latter is correct, find all matches with your basic pattern and from the array of matches take the first and the last one, eg:

//Match using a simpler regex
var matches = yourMultiLineText.match(yourRegex);
//Store the result here
var result;
//Make sure that there are at least 2 matches in total for this to make sense.
if(matches.length > 1){
   //Grab the first and the last match.
   result = [matches[0], matches[matches.length - 1]];
} else {
   result = [];
}