如何将DataTables pagingType:input属性设置为只读？

$.fn.dataTableExt.oPagination.input = {
    "fnInit": function (oSettings, nPaging, fnCallbackDraw) {
        var nInput = document.createElement('input');
        nInput.type = 'text';
        nInput.style.width = '50px';
        nInput.style.display = 'inline-block';
        nInput.value = oSettings._iDisplayStart + 1;
        nInput.onkeypress = function (e) {
            if (e.keyCode == 13) {
                var iNewStart = oSettings._iDisplayLength * (this.value - 1);
                if (iNewStart >= oSettings.fnRecordsDisplay()) {
                    iNewStart = 0;
                }
                oSettings._iDisplayStart = iNewStart;
                fnCallbackDraw(oSettings);
            }
        };
        nPaging.appendChild(nInput);
    },

    "fnUpdate": function (oSettings, fnCallbackDraw) {
        var oPaging = oSettings.oInstance.fnPagingInfo();
        var nInput = $(oSettings.aanFeatures.p)[0].getElementsByTagName('input')[0];
        nInput.value = oPaging.iPage + 1;
    }
};

$('#example').DataTable({
    pagingType: 'input',
    oPaginate: {
        "sPaginationType": "input"
    }
});