$("#dataGrid").jqGrid({
    ...
    colModel: [

        { name: 'subject', index: 'subject', sortable: true, classes: 'ui-ellipsis', width: columnWidths.subject,
            sorttype: function (cell) { return sortable(cell); } }
        ],
    ...               

});

...

function makeSortable(s)
{
    var r = s.toLowerCase();
    var diacritics = [
        [/[\340-\346]/g, 'a'],
        [/[\350-\353]/g, 'e'],
        [/[\354-\357]/g, 'i'],
        [/[\362-\370]/g, 'o'],
        [/[\371-\374]/g, 'u'],
        [/[\361]/g, 'n'],
        [/[\347]/g, 'c']
    ];

    for (var i = 0; i < diacritics.length; i++)
    {
        r = r.replace(diacritics[i][0], diacritics[i][1]);
    }
    return r;
}

Currently the sorttype property of a column defines the type of the column for appropriate sorting.

Possible values include int/integer – for sorting integer ; float/number/currency – for sorting decimal numbers ; date – for sorting date and text – for text sorting.

I have a need for case, punctuation and accent insensitive text sorting. Does anyone know how to use a custom sorting fuction to achieve this?

For example, currently jqGrid sorts a column in this order:

1. …
2. Cross-border reorganization
3. Crystallization of…
4. Crédit d'impôt …
5. …
6. Draft Guidance on …
7. Dubai Investment
8. Décisions récentes
9. …
10. Lutte contre les planifications fiscale
11. L’Institut des Cadres Fiscaliste: …
12. Majoration fiscale …
13. …
14. World Tour …
15. École de hautes …
16. …

The requirement is to have a sortable column in this order:

1. …
2. Crédit d'impôt …
3. …
4. Cross-border reorganization
5. Crystallization of…
6. …
7. Décisions récentes
8. …
9. Draft Guidance on …
10. Dubai Investment
11. …
12. École de hautes …
13. …
14. L’Institut des Cadres Fiscaliste: …
15. …
16. Lutte contre les planifications fiscale
17. Majoration fiscale …
18. …
19. World Tour …
20. …