The question is very simple, but I still don't know the exact meaning. In Angular 5.2 FormBuilder group method,it shows. (method) FormBuilder.group(controlsConfig: { [key: string]: any; }, extra?: { [key: string]: any; } | null): FormGroup How to interpret this signature? It receive an object named controlsConfig with key as string datatype, value as any datatype? And an optional object parameter with name 'extra' with (key is string datatype, value is any datatype) or with extra parameter value = null? Continue reading...
