Adds a "select all" and "deselect" all link to a taxonomy or category box while editing a WordPress post. addSelectAlltoTaxGroup($key) where $key = taxonomy name.

addSelectAlltoTaxGroup.js

jQuery(document).ready(function($) {

    addSelectAlltoTaxGroup( 'region' );
    addSelectAlltoTaxGroup( 'program' );
    
    function addSelectAlltoTaxGroup( key )
    {
        var selectAll = "<span class=\"my-selector\">&nbsp; | <a href=\"#"+key+"-adder\" id=\""+key+"-select-all\">Select All</a></span>";
        var deselectAll = "<span class=\"my-selector\">&nbsp; | <a href=\"#"+key+"-adder\" id=\""+key+"-deselect-all\">Deselect All</a></span>";

        $('#taxonomy-'+key+' #'+key+'-adder h4').append( selectAll );
        $('#'+key+'-deselect-all').live( 'click', function() {
            $('#'+key+'-all :checkbox').each( function() { $(this).prop('checked', false ); });
            $('#taxonomy-'+key+' #'+key+'-adder h4 span.my-selector').remove();
            $('#taxonomy-'+key+' #'+key+'-adder h4').append( selectAll );
            return false;
        })
        $('#'+key+'-select-all').live( 'click', function() {
            $('#'+key+'-all :checkbox').each( function() { $(this).prop('checked', true ); });
            $('#taxonomy-'+key+' #'+key+'-adder h4 span.my-selector').remove();
            $('#taxonomy-'+key+' #'+key+'-adder h4').append( deselectAll );
            return false;
        })
    }
});