I can get the source of a regex when it's defined separately. For example:
let r1 = new RegExp("el*");
console.log(r1.source);
// el*Or:
let r2 = /el*/;
console.log(r2.source);
// el*Is there a way to extract that if the regex isn't defined separately? For example, something along the lines of:
let m = "Hello".match(/el*/);
console.log(m.source?);
No,
quoting the documents of the match() function
Return value
An Array whose contents depend on the presence or absence of the global (g) flag, or null if no matches are found.
So the return value is an array (you can test it by Array.isArray(m)// true)
However, the returned array has some extra information about the ocurred match (like groups, index and original input) but none of them include the original regex used to get the match
So there is no way to get that information from the match because its not returned by the matching function
The match result by itself cannot lead to the original regex, simply because different regexes can lead to the same result, even on the same string. Take for example the string "abcd" - all the following regexes: /abcd/, /a..d/ /a.*/ and many more, would match the string exactly the same way.
The only way you could retrive the original regex is if a reference to the regex was literally stored by the match() method inside the returned object. There is no reason to think that's the case, but you can implement your own match function that would do. Something like
function myMatch(str, regex) {
var match = str.match(regex);
if (match === null) {
match = [null];
}
match.source = regex;
return match;
}