Method updateGroup

docs/app/js/sanddance-app.js:12619–12628

(partialGroup, groupIndex)

            return group;
        }
        updateGroup(partialGroup, groupIndex) {
            const groups = [
                ...this.state.groups
            ];
            const group = Object.assign(Object.assign({}, groups[groupIndex]), partialGroup);
            groups[groupIndex] = group;
            this.setState({
                groups
            });
        }
        addGroup() {
            const groups = [
                ...this.state.groups