A comparison of how to safely iterate over all regex matches, when accepting an arbitrary regex.

regexp-iterate.js

// Using native JavaScript...

function getMatches(str, regex) {
    var matches = [];
    var match;

    if (regex.global) {
        regex.lastIndex = 0;
    } else {
        regex = new RegExp(regex.source, 'g' +
            (regex.ignoreCase ? 'i' : '') +
            (regex.multiline ? 'm' : '') +
            (regex.sticky ? 'y' : ''));
    }

    while (match = regex.exec(str)) {
        // If you want to use regex.lastIndex in this loop, you'd need more
        // code here to fix IE < 9

        matches.push(match);

        if (regex.lastIndex === match.index) {
            regex.lastIndex++;
        }
    }

    return matches;
}

xregexp-iterate.js

// Using XRegExp...

function getMatches(str, regex) {
    return XRegExp.forEach(str, regex, function(match) {
        this.push(match);
    }, []);
}

So you’re using XRegExp.forEach as if it was reduce? Cool :)

@mathiasbynens, XRegExp.forEach always returns its callback's context (this). You can set the context either by using a bind method or, as I did in this example, via the fourth argument.