xregexp.js
function isQuantifierNext(pattern, pos, flags) {
        return nativ.test.call(
            flags.indexOf('x') > -1 ?
                // Ignore any leading whitespace, line comments, and inline comments
                /^(?:\s+|#.*|\(\?#[^)]*\))*(?:[?*+]|{\d+(?:,\d*)?})/ :
                // Ignore any leading inline comments
                /^(?:\(\?#[^)]*\))*(?:[?*+]|{\d+(?:,\d*)?})/,
            pattern.slice(pos)
        );
    }
function isQuantifierNext(pattern, pos, flags) {
        return nativ.test.call(
            flags.indexOf('x') > -1 ?
                // Ignore any leading whitespace, line comments, and inline comments
                /^(?:\s+|#.*|\(\?#[^)]*\))*(?:[?*+]|{\d+(?:,\d*)?})/ :
                // Ignore any leading inline comments
                /^(?:\(\?#[^)]*\))*(?:[?*+]|{\d+(?:,\d*)?})/,
            pattern.slice(pos)
        );
    }
function isQuantifierNext ( pattern , pos , flags ) { return nativ . test . call ( flags . indexOf ( 'x' ) > - 1 ? // Ignore any leading whitespace, line comments, and inline comments / ^(?:\s+|#.*|\(\?#[^)]*\))*(?:[?*+]|{\d+(?:,\d*)?}) / : // Ignore any leading inline comments / ^(?:\(\?#[^)]*\))*(?:[?*+]|{\d+(?:,\d*)?}) / , pattern . slice ( pos ) ) ; }
Checks whether the next nonignorable token after the specified position is a quantifier.

@private
@param {String} pattern Pattern to search within.
@param {Number} pos Index in `pattern` to search at.
@param {String} flags Flags used by the pattern.
@returns {Boolean} Whether the next token is a quantifier.
Checks whether the next nonignorable token after the specified position is a quantifier .