Question

How can we have global Expand/Collapse for JQGrid when we have rows grouped on some field?

On expanding, it should expand all groups and on collapsing all groups should be collapsed.

Answer 1

You can set default value of the groupCollapse property of the groupingView parameter of jqGrid in the same way like you set any other default parameter:

$.extend($.jgrid.defaults, {
    groupingView: {
        groupCollapse: true
    }
});

UPDATED: After additional explanation in the comments I can me imagine that in some cases it can has the behavior when all groups will be expanded/collapsed if any from the groups will be expanded/collapsed.

var $grid = $("#list"), inOnClickGroup = false;

$grid.jqGrid({
    // ... other options
    grouping: true,
    onClickGroup: function (hid) {
        var idPrefix = this.id + "ghead_", id, i, l,
            groups = this.p.groupingView.sortnames[0];

        if (!inOnClickGroup && hid.length > idPrefix.length &&
                hid.substr(0, idPrefix.length) === idPrefix) {
            id = Number(hid.substr(idPrefix.length));
            if (typeof (groups[id]) !== "undefined") {
                inOnClickGroup = true; // set to skip recursion
                for (i = 0, l = groups.length; i < l; i++) {
                    if (i !== id) {
                        $(this).jqGrid('groupingToggle', this.id + 'ghead_' + i);
                    }
                }
                inOnClickGroup = false;
            }
        }
    }
});

See the demo.