`pick` method returns the first match from a filter

[shehabadel]

I am trying to clean a URL and only keep some parameters that I need in order to parse them
so I was using pick method providing it the url, and the filter which is a regex test method
here I am testing to check if the key in the query parameter matches the regular expression

const groupRegex = new RegExp('^(GRP_)[a-zA-Z0-9/-]','g');
export const parseGroups= (url:string)=>{
    let pickedURL = qs.pick(url,(key,value)=>groupRegex.test(key));
    console.log(pickedURL);
}
var url=`http://localhost:3000/tat?GRP_Bob[]=SW&GRP_sa[]=QW&GRP_sa[]=AA&projects[]=MP,PM&releases[]=2021.4,2022.1`
parseGroups(url)

for example http://localhost:3000/tat?GRP_Bob[]=SW&GRP_sa[]=QW&GRP_sa[]=AA&projects[]=MP,PM&releases[]=2021.4,2022.1
it should return http://localhost:3000/tat?GRP_Bob=SW&GRP_sa=QW&GRP_sa=AA
yet it only tests for the first request parameter only and logs
http://localhost:3000/tat?GRP_Bob%5B%5D=SW

I am trying to clean the url from any other parameters that doesn't match my regular expression
so I can parse the URL and extract the object
so it can be like this for example

{
       GRP_Bob:["SW"],
       GRP_sa:["QW","AA"]
 }

Instead of having other parameters parsed also which are not necessary. I know I can just parse the url normally, and then loop on the returned query object, and remove any key that doesn't match the regex, but is there anything wrong I am doing in the above snippet?

UPDATE:
I changed the filter function to be (key,value)=>key.startsWith('GRP_'))

export const parseGroups= (url:string)=>{
    let pickedURL = qs.pick(url,(key,value)=>key.startsWith('GRP_'));
    console.log(pickedURL);
    let parsedURL = qs.parseUrl(pickedURL)
    console.log(parsedURL.query)
}
var url=`http://localhost:3000/tat?GRP_Bob[]=SW&GRP_sa[]=QW&GRP_sa[]=AA&projects[]=MP,PM&releases[]=2021.4,2022.1`
parseGroups(url)

and the pickedURL logged this http://localhost:3000/tat?GRP_Bob%5B%5D=SW&GRP_sa%5B%5D=QW&GRP_sa%5B%5D=AA which is likely to be correct.
it came out like that

GRP_Bob[]: "SW"
GRP_sa[]: (2) ['QW', 'AA']

So I am confused actually what's going on with the regular expression approach, and why the keys in the second approach have [] in it?

[shehabadel]

After asking on StackOverflow, thanks to Adam Thomas for solving the regular expression approach.

Ah yeh! This one is a rare gotcha and totally unexpected every time I see it.
RegExp actually has state. See Why does JavaScript's RegExp maintain state between calls? and Why does Javascript's regex.exec() not always return the same value?.
In your case, you don't need the g flag, so removing that should also fix your problem since that makes the regex stateless.

So here is the code snippet now

const groupRegex = new RegExp('^(GRP_)[a-zA-Z0-9/-]');
export const parseGroups= (url:string)=>{
    let pickedURL = qs.pick(url,(key,value)=>groupRegex.test(key));
    console.log(pickedURL);
    let parsedURL = qs.parseUrl(pickedURL)
    console.log(parsedURL.query)        
}
var url=`http://localhost:3000/tat?GRP_Bob[]=SW&GRP_sa[]=QW&GRP_sa[]=AA&projects[]=MP,PM&releases[]=2021.4,2022.1`
parseGroups(url)

pickedUrl logs like this, which I don't really understand why [] was changed to %5B%5D
http://localhost:3000/tat?GRP_Bob%5B%5D=SW&GRP_sa%5B%5D=QW%2CAA
while parsedURL logs like this, which I believe was affected since the keys have [] characters in it.
{GRP_Bob[]: 'SW', GRP_sa[]: 'QW,AA'}

[shehabadel]

Well I partially solved it by passing the following options argument

let parsedURL = qs.parseUrl(url,{arrayFormat: 'bracket-separator', arrayFormatSeparator:','})

I still have no idea why pick method converts [] to %5B5D