GroupByRule

groupByRule({
    id: string;
    groupFn: (item) => string | number;
    sortGroupIdFn?: (group) => string | number;
    groupIdSortDirection?: SortDirection;
    sticky?: {
        header?: string | string[];
        footer?: string | string[];
    };
    label?: string;
    hidden?: boolean;
})

Prop	Description	Default	Required
id	Every groupBy rule must have a unique string id.		✓
groupFn	A callback that returns a string or number. Items with the same value will be grouped together.		✓
sortGroupIdFn	While any sortBy rules will operate on the items first, sortGroupIdFn allows you to sort the groups themselves.
sticky	Specify group ids that should be stickied to the top or bottom of the results.
label	Optional label for your client to display.
hidden	Optional display value for your client to display.	false

tip

• Only a single groupBy rule can be active at one time.
• If the Finder instance has requireGroup enabled and no groupBy rule is active, the first rule in the stack will be considered active.
• If you want a group of premium items to always appear first in the results, you can set sticky: {header: 'premium_id' }. If an array is provided, the order will be preserved. ( i.e: sticky: { header: ['premium_id', 'subpremium_id']}).