Regex returns string undefined

Question

I am trying to extract hash value from an magnet link but it returns undefined

var tesst = \"magnet:?xt=urn:btih:2B78EDFDDC87DC9605FB285997A80B787888C19         


        

Answer 1

just mark what you want with capturing group:

/^magnet:\?xt=urn:btih:([a-z\d]{40})\&$/im

Also I recomend to not use regexp here.
Try followed:

tesst.split(':')[3].slice(0, -1);

slice(0, -1) used for remove last '&', you can use any other method, like slice(0, 40), replace(/[^\w]/g, '') or any other.