Angular 6 - compare two observables lengths
问题 Is there a way to compare the current length of two observables? EDIT: It is to compare the arrays withing the observables. I want to compare all the elements count withing them(See example below). At the point I am trying to do it, they are already completely loaded. Not waiting on any data. For example I want to do: if (array1.length < array2.length) { array1.foreach(item => item.isSelected = true); I tried using pipe, map, tap , but they resolve after some time and don't work for me. I