Sizzle.selectors.match/leftMatch

var Expr = Sizzle.selectors = {
    match : {
        ID: /#((?:[\w\u00c0-\uFFFF\-]|\\.)+)/,
        CLASS: /\.((?:[\w\u00c0-\uFFFF\-]|\\.)+)/,
        NAME: /\[name=['"]*((?:[\w\u00c0-\uFFFF\-]|\\.)+)['"]*/,
        ATTR: /\[\s*((?:[\w\u00c0-\uFFFF\-]|\\.)+)\s*(?:(\S?=)\s*(?:(['"])(.*?)\3|(#?(?:[\w\u00c0-\uFFFF\-]|\\.)*)|)|)\s*\]/,
        TAG: /^((?:[\w\u00c0-\uFFFF\*\-]|\\.)+/,
        CHILD: /:(only|nth|last|first)-child(?:\(\s*(even|odd|?:[+\-]?\d+|(?:[+\-]?\d*)?n\s*\d+)?))\s*\))?/,
        POS: /:(nth|eq|gt|lt|first|last|even|odd)(?:\((\d*)\))?(?=[^\-]|$)/,
        PSEUDO: /:((?:[\w\u00c0-\uFFFF\-]|\\.)+)(?:\((['"]?)((?:\([^\)]+\)|[^\(\)]*)+)\2\))?/
    }
}

var origPOS = Expr.match.POS,
    fescape = function(all, num) {
        return "\\" + (num - 0 + 1);
    };

for ( var type in Expr.match ) {
    Expr.match[ type ] = new RegExp( Expr.match[ type ].source + (/(?![^\[]*\])(?![^\(]*\))/.source) );
    Expr.leftMatch[ type ] = new RegExp ( /(^(?:.|\r|\n)*?)/.source + Expr.match[ type ].source.replace(/\\(\d+)/g, fescape) );
}