proc sortCommand {nodeValueCommand options node1 node2} {
    # get the values to compare
    #
    set value1 [{*}[string map [list %N $node1] $nodeValueCommand]];
    set value2 [{*}[string map [list %N $node2] $nodeValueCommand]];

    # care for the nocase option
    #
    if {"-nocase" in $options} {
        set value1 [string tolower $value1];
        set value2 [string tolower $value2];
    }

    # compare in dictionary style
    #
    if {"-dictionary" in $options} {
        if {$value1 eq $value2} {
            return 0;
        }

        set list [lsort -dictionary [list $value1 $value2]];

        if {$value1 eq [lindex $list 0]} {
            return -1;
        }

        return 1;
    }

    # compare non-numerical values
    #
    if {   ("-real" ni $options && "-integer" ni $options)
        || ![string is double -strict $value1]
        || ![string is double -strict $value2]} {
        return [string compare $value1 $value2];
    }

    # compare numerical values
    #
    if {$value1 == $value2} {
        return 0;
    } elseif {$value1 > $value2} {
        return 1;
    }

    return -1;
}

proc sortNodesByCommand {parentNode nodeValueCommand args} {
    # get the child nodes and sort them
    #
    set childNodes  [$parentNode childNodes];
    set sortedNodes [lsort \
        {*}$args \
        -command [list sortCommand $nodeValueCommand $args] \
        $childNodes \
    ];

    if {$sortedNodes eq $childNodes} {
        return;
    }

    # remove all child nodes from the parent node
    #
    foreach childNode $childNodes {
        $parentNode removeChild $childNode;
    }

    # add the child nodes in the new order
    #
    foreach childNode $sortedNodes {
        $parentNode appendChild $childNode;
    }

    return;
}

proc sortNodesByName {parentNode args} {
    sortNodesByCommand $parentNode {%N nodeName} {*}$args -dictionary;
}

proc sortNodesByValue {parentNode args} {
    sortNodesByCommand $parentNode {%N nodeValue} {*}$args;
}

proc sortNodesByText {parentNode args} {
    sortNodesByCommand $parentNode {%N text} {*}$args -dictionary;
}

proc sortNodesByAttribute {parentNode attribute args} {
    sortNodesByCommand $parentNode {%N getAttribute $attribute} {*}$args;
}

# examples
#
package require tdom;

set dom [dom parse -html [tDOM::xmlReadFile $htmlFile]];
set doc     [$dom documentElement];
set head    [$doc firstChild];

sortNodesByName $head;
sortNodesByCommand $body {llength [%N childNodes]};