this.ProjectGroupList = this.groupBy(this.ProjectList, function(item) { return [item.ParentID]; });
groupBy: function(array, f) { let groups = {}; array.forEach(function(o) { let group = JSON.stringify(f(o)); groups[group] = groups[group] || []; groups[group].push(o); }); return Object.keys(groups).map(function(group) { return groups[group]; }); },