Javascript Regex and Submatches

Question

Why do javascript sub-matches stop working when the g modifier is set?

var text = 'test test test test';

var result = text.match(/t(e)(s)t/);
// result: ["test", "e", "s"]

the above works fine... [1] is e and [2] is s... perfect

var result = text.match(/t(e)(s)t/g);
// ["test", "test", "test", "test"]

the above it screwed... it ignores my sub-matches

var result = text.match(/test/g);
for (i in result) {
    console.log(result[i].match(/t(e)(s)t/));
}
/*
["test", "e", "s"]
["test", "e", "s"]
["test", "e", "s"]
["test", "e", "s"]
*/

is the above the only valid solution?

thanks to htw the proper way to do this would be the following:

var pattern = new RegExp(/t(e)(s)t/g);
while (match = pattern.exec(text))
{
    console.log(match);
}

Answer 1

Using String's match() function won't return captured groups if the global modifier is set, as you found out.

In this case, you would want to use a RegExp object and call its exec() function. String's match() is almost identical to RegExp's exec() function…except in cases like these. If the global modifier is set, the normal match() function won't return captured groups, while RegExp's exec() function will. (Noted here, among other places.)

Another catch to remember is that exec() doesn't return the matches in one big array—it keeps returning matches until it runs out, in which case it returns null.

So, for example, you could do something like this:

var pattern = /t(e)(s)t/g;  // You could also use "new RegExp(/t(e)(s)t/g);"
var match;    

while (match = pattern.exec(text))
{
    // Do something with the match (["test", "e", "s"]) here...
}

You can find information on how to use RegExp objects on W3Schools (specifically, here's the documentation for the exec() function).