How can I match a specific parameter from URL?

Question

I have a string (which is the value of href attribute) like this:

var url = '/myweb/search?s=islamic_sources&q=test';

It also sometimes looks like these:

url = '/myweb/search?q=test';
url = '/myweb/search?q=test&g=sth';

Here

^[^?]+.*?&?q=([^$|&]+)

is what I've tried so far, and I need to match test in those three lines. But sadly seems $ doesn't mean end of line in my pattern. How can I fix it?

It is not quite clear why you chose this regex. Try [`\bq=([^&]+)(?!.*\?)`](https://regex101.com/r/xuRvUs/1) (note `\n` added in the demo since it is a multiline string). The `(?!.*\?)` here will fail all matches outside a query string. — Wiktor Stribiżew, Mar 27 '17 at 12:18
Regex is tricky, but here's how someone else on SO accesses the query variables in a similarly formatted string, I hope it helps! http://stackoverflow.com/questions/901115/how-can-i-get-query-string-values-in-javascript — Aaron Belchamber, Mar 27 '17 at 12:20
follow this - https://gist.github.com/marmeladze/f693501707940b1ea1af433c327800a9 — marmeladze, Mar 27 '17 at 12:25
@WiktorStribiżew your pattern [works as well](https://regex101.com/r/xuRvUs/2). But do you know why it doesn't work in [JS](https://jsfiddle.net/5nL7psof/) ? *(it doesn't work when I remove `\n` either)* — Martin AJ, Mar 27 '17 at 12:35
What a strange piece of code... [Here is the correct one](https://jsfiddle.net/5nL7psof/2/) (without error checking). — Wiktor Stribiżew, Mar 27 '17 at 12:39
@WiktorStribiżew your code returns the matched thing. but I want that url with a new value instead of matched thing. — Martin AJ, Mar 27 '17 at 12:40
@WiktorStribiżew yes, now that's correct. But that's odd, because your code is exactly the same as mine. Just I've used `\K` in the pattern and removed `q=` in the substitution. — Martin AJ, Mar 27 '17 at 12:44
Yes, but JavaScript regex engine does not support the PCRE operator `\K` — Wiktor Stribiżew, Mar 27 '17 at 12:45

score 0 · Answer 1 · answered Mar 27 '17 at 12:19

You can simply use:

url.match(/q=([^&]*)/)

This will return an array. If not empty, test will be at index 1.

var url1 = '/myweb/search?s=islamic_sources&q=test';
var url2 = '/myweb/search?q=test';
var url3 = '/myweb/search?q=test&g=sth';

console.log(url1.match(/q=([^&]*)/)[1]);
console.log(url2.match(/q=([^&]*)/)[1]);
console.log(url3.match(/q=([^&]*)/)[1]);

score 0 · Answer 2 · answered Mar 27 '17 at 12:19

the regex is /q=[^&]+/ and execute it in the url, then take first match, split it on =, then take second part.

I created it as a function below.

var url1 = '/myweb/search?s=islamic_sources&q=test';
var url2 = '/myweb/search?q=test';
var url3 = '/myweb/search?q=test&g=sth';

function retMatch(url){
  var re=/q=[^&]+/;
  return re.exec(url1)[0].split('=')[1];
}
console.log(retMatch(url1));
console.log(retMatch(url2));
console.log(retMatch(url3));

How can I match a specific parameter from URL?

2 Answers2