QUESTION
I think I must just be really tired, because this should be really simple, but it's just not working for me. I want to match a portion of a string using a regex and then access that parenthesized substring.
var myString = "something format_abc"; // I want "abc"
var arr = /(?:^|\s)format_(.*?)(?:\s|$)/(myString);
console.log(arr); // prints: [" format_abc", "abc"] .. so far so good.
console.log(arr[1]); // prints: undefined (???)
console.log(arr[0]); // prints: format_undefined (!!!)
can anyone see what I'm doing wrong?
Update: I've discovered that there was nothing wrong with the regex code above: the actual string which I was testing against was this:
"date format_%A"
Reporting that "%A" is undefined seems a very strange behaviour, but not directly related to this question, so I've opened a new one here. Thanks to everyone who responded.
Update: The issue was that console.log takes its parameters like a printf statement, and since the string I was logging ("%A") had a special value, it was trying to find the value of the next parameter.
Since this was just a silly bug on my part, I'll now close this question.
ANSWER
You can access capturing groups like this:
var myString = "something format_abc";
var myRegexp = /(?:^|\s)format_(.*?)(?:\s|$)/g;
var match = myRegexp.exec(myString);
alert(match[1]); // abc
And if there are multiple matches you can iterate over them:
match = myregexp.exec(myString);
while (match != null) {
// matched text: match[0]
// match start: match.index
// capturing group n: match[n]
}
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