CreateGroupLayer = function (json, group, parentState)
{
    if (!group)
    {
        // Return a default group state object
        return {
            i: 0, // Current layer array iterator
            layers: json.layers, // Current array of layers
            // Values inherited from parent group
            name: '',
            opacity: 1,
            visible: true,
            x: 0,
            y: 0
        };
    }

    // Compute group layer x, y
    var layerX = group.x + GetFastValue(group, 'startx', 0) * json.tilewidth + GetFastValue(group, 'offsetx', 0);
    var layerY = group.y + GetFastValue(group, 'starty', 0) * json.tileheight + GetFastValue(group, 'offsety', 0);

    // Compute next state inherited from group
    return {
        i: 0,
        layers: group.layers,
        name: parentState.name + group.name + '/',
        opacity: parentState.opacity * group.opacity,
        visible: parentState.visible && group.visible,
        x: parentState.x + layerX,
        y: parentState.y + layerY
    };
}
Parse a Tiled group layer and create a state object for inheriting.

@function Phaser.Tilemaps.Parsers.Tiled.CreateGroupLayer
@since 3.21.0

@param {object} json - The Tiled JSON object.
@param {object} [group] - The current group layer from the Tiled JSON file.
@param {object} [parentState] - The state of the parent group (if any).

@return {object} A group state object with proper values for updating children layers.