Function augment

docs/tests/v2/es6/js/sanddance.js:139054–139082

* Attaches extended data and `XRegExp.prototype` properties to a regex object. * * @private * @param {RegExp} regex Regex to augment. * @param {Array} captureNames Array with capture names, or `null`. * @param {String} xSource XRegExp pattern used to generate `regex`, or `null` if N/A. * @para

(regex, captureNames, xSource, xFlags, isInternalOnly)

 * @returns {RegExp} Augmented regex.
 */
function augment(regex, captureNames, xSource, xFlags, isInternalOnly) {
    var p = void 0;

    regex[REGEX_DATA] = {
        captureNames: captureNames
    };

    if (isInternalOnly) {
        return regex;
    }

    // Can't auto-inherit these since the XRegExp constructor returns a nonprimitive value
    if (regex.__proto__) {
        regex.__proto__ = XRegExp.prototype;
    } else {
        for (p in XRegExp.prototype) {
            // An `XRegExp.prototype.hasOwnProperty(p)` check wouldn't be worth it here, since this
            // is performance sensitive, and enumerable `Object.prototype` or `RegExp.prototype`
            // extensions exist on `regex.prototype` anyway
            regex[p] = XRegExp.prototype[p];
        }
    }

    regex[REGEX_DATA].source = xSource;
    // Emulate the ES6 `flags` prop by ensuring flags are in alphabetical order
    regex[REGEX_DATA].flags = xFlags ? xFlags.split('').sort().join('') : xFlags;

    return regex;
}

/**
 * Removes any duplicate characters from the provided string.