title: Which Rxjs operator to choose for multiple observables
body: <p>My question can be obvious but I’m new at RxJs and get lost in the descriptions of dozen of operators.</p>
  
  <p>I have an angular 8 project. I have 5 observables. I need to put all data from them into one stream. As result I expect sorted list or array , sort criteria- by date. And also I need to recognize in my html-template which data type every object is. I have read about mergeMap, forkJoin . But can’t choose right for my task. Please help!</p>