JSFiddle - React, Tailwind, and code Playground

JavaScript

$.jgrid.extend({
    nextCell : function (iRow, iCol) 
    {
        return this.each(function ()
        {
            var $t = this, nCol = false;
            if (!$t.grid || $t.p.cellEdit !== true) {return;}
            
            // trying to find next editable column on the right from actual selected cell
            for (var i = iCol + 1; i < $t.p.colModel.length; i++)
            {
                if ( $t.p.colModel[i].editable === true )
                {
                        nCol = i;
                        break;
                }
            }
            
            // if such one doesn't exist, trying to find next editable column on the left
            if(nCol === false)
            {
                for (var i = 0; i < (iCol -1); i++)
                {
                    if ( $t.p.colModel[i].editable === true )
                    {
                        nCol = i;
                        break;
                    }
                }
            }
            
            if(nCol !== false)
            {
                if (nCol > iCol)    // if it is in the same row
                    $($t).jqGrid("editCell", iRow, nCol, true);
                else    //edit in the nex row
                    $($t).jqGrid("editCell", (iRow + 1) , nCol, true);
            }
            else
            {
                if ($t.p.savedRow.length > 0)
                    $($t).jqGrid("saveCell", iRow, iCol);
            }
        });
    },
    prevCell : function (iRow, iCol)
    {
        return this.each(function ()
        {
            var $t = this, nCol = false;
            if (!$t.grid || $t.p.cellEdit !== true) {return;}
            
            // trying to find next editable column on the left from actual selected cell
            for (var i= iCol-1; i >= 0; i--) 
            {
                if ( $t.p.colModel[i].editable === true)
                {
                    nCol = i;
                    break;
                }
            }
     ...