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Код
var isset= function( value ){
    return( typeof value !== 'undefined' )&&( value !== null );
}

var jpath= function( path ){ // version 2.0b1
    var nodes= [ this ];
    var collector= [];
    var paths= [];
    while( path ){
        var m= /^\s*(?:([\[\]])|(\/\/|[-.+^\/])([\w#$-]+|\*)?(?:\:([\w-]+))?)\s*(.*?)$/.exec( path );
        if( !m ) throw 'jpath error: broken expression "' + path + '"';
        var scope= m[1];
        var axis= m[2];
        var name= m[3];
        var klass= m[4];
        path= m[5];
        switch( scope ){
            case '[':
                paths.unshift( path );
                collector.unshift( [] );
            break;
            case ']':
                if( !paths ) throw 'jpath scope error';
                if( nodes.length ){
                    path= paths[0];
                    collector[0]= collector[0].concat( nodes );
                } else {
                    nodes= collector.shift();
                    paths.unshift();
                }
            break;
            default:
                var newNodes= [];
                switch( axis ){
                    case '+':
                    case '-':
                    case '^':
                        var prop= {
                            '^': 'parentNode',
                            '+': 'nextSibling',
                            '-': 'previousSibling'
                        }[ axis ];
                        if( name ){
                            name= name.toUpperCase();
                            var checkNode= ( name === '*' )
                                ? function( node ){ return node.nodeType === 1 }
                                : function( node ){ return node.nodeName === name }
                        } else var checkNode= function( ){ return true }
                        var checkClass= klass
                            ? function( node ){ return RegExp( '\\b' + klass + '\\b' ).test( node.className ) }
                            : function( ){ return true }
                        for( var i= 0; i < nodes.length; ++i ){
                            var node= nodes[i];
                            while( node= node[ prop ] )
                                if( checkNode( node ) && checkClass( node ) ){
                                    newNodes.push( node );
                                    break;
                                }
                        }
                    break;
                    case '/':
                        if( name ){
                            name= name.toUpperCase();
                            checkNode= ( name === '*' )
                                ? function( node ){ return node.nodeType === 1 }
                                : function( node ){ return node.nodeName === name }
                        } else var checkNode= function( ){ return true }
                        var checkClass= klass
                            ? function( node ){ return RegExp( '\\b' + klass + '\\b' ).test( node.className ) }
                            : function( ){ return true }
                        for( var i= 0; i < nodes.length; ++i ){
                            var childs= nodes[i].childNodes;
                            for( var j= 0; j < childs.length; ++j ){
                                var node= childs[ j ];
                                if( checkNode( node ) && checkClass( node ) ) newNodes.push( node );
                            }
                        }
                    break;
                    case '//':
                        for( var i= 0; i < nodes.length; ++i ){
                            var node= nodes[i];
                            var descs= node.getElementsByTagName( name || '*' );
                            if( !name ){
                                var proc= function( node ){
                                    var childs= node.childNodes;
                                    for( var j= 0; j < childs.length; ++j )
                                        newNodes.push( childs[j] );
                                }
                                proc( node );
                                for( var j= 0; j < descs.length; ++j ) proc( descs[j] );
                            } else if( klass ){
                                for( var j= 0; j < descs.length; ++j ){
                                    var node= descs[j];
                                    if( RegExp( '\\b' + klass + '\\b' ).test( node.className ) )
                                        newNodes.push( node );
                                }
                            } else {
                                for( var j= 0; j < descs.length; ++j )
                                    newNodes.push( descs[j] );
                            }
                        }
                    break;
                    case '.':
                        if( !name ){
                            var proc= function( node ){
                                for( var i in node ){
                                    var val= node[ i ];
                                    if( isset( val ) ) newNodes.push( val );
                                }
                            }
                        } else if( name === '*' ){
                            var proc= function( node ){
                                for( var i in node ){
                                    var val= node[ i ];
                                    if( val ) newNodes.push( val );
                                }
                            }
                        } else {
                            var proc= function( node ){
                                var val= node[ name ];
                                if( isset( val ) ) newNodes.push( val );
                            }
                        }
                        for( var i= 0; i < nodes.length; ++i ) proc( nodes[i] );
                    break;
                } // switch axis
                nodes= newNodes;
            break;
        } // switch scope
    } // while path
    return nodes;
} // jpath