typescript - Angular 4 Firebase Observable with .map() apears two times on refresh and not reversed -


i using angular 4 firebase , angularfire. want display on html code first top 10 users, code is

 export class homefillercomponent implements oninit {   topusers: observable<any>;   constructor(db: angularfiredatabase,public authservice: authservice) {           this.topusers = db.list('users', {         query: {          orderbychild: "totalscore",          limittolast: 10,         }         }).map((topusers) => {console.log(topusers);         return topusers.reverse();})       }

my firebase database is:

"users" : {     "test1" : {       "totalscore" : 50,       "username" : "test1"     },     "test2" : {       "totalscore" : 30,       "username" : "test2"     },     "test3" : {       "totalscore" : 20,       "username" : "test1"     },     "test4" : {       "totalscore" : 10,       "username" : "test1"     },     "zekes" : {      "totalscore" : 14,      "username" : "zekes"       }   }

when navigate in angular 4 app works fine.however when refrest page 2 console.log(a) 1 reversed object , second 1 not reversed object.so html displays not reversed object. have idea of wrong?? happens when refresh page. console.log(a) when refresh page.this <code>console.log(a)</code> when refresh page.


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