How to create timer in angular2

Question

I need a timer in Angular 2  which tick after a time interval and do some task  may be call some functions    How to do this with Angular 2

User · Answer

Set Timer and auto call service after certain time    Initialize from ngInit ngOnInit    void  this getNotifications      getNotifications         setInterval      gt   this getNewNotifications           60000       60000 milliseconds interval    getNewNotifications         this notifyService getNewNotifications   subscribe          data   gt       call back            error   gt

User · Answer

I faced a problem that I had to use a timer  but I had to display them in 2 component same time  same screen  I created the timerObservable in a service  I subscribed to the timer in both component  and what happened  It won t be synched  cause new subscription always creates its own stream   What I would like to say  is that if you plan to use one timer at several places  always put  publishReplay 1  refCount   at the end of the Observer  cause it will publish the same stream out of it every time   Example   this startDateTimer   Observable combineLatest this timer  this startDate    localTimer  startDate    gt      return this calculateTime startDate      publishReplay 1  refCount

User · Answer

You can simply use setInterval utility and use arrow function as callback so that this will point to the component instance   For ex    this interval   setInterval       gt            call your functions like      this getList        this updateInfo          Inside your ngOnDestroy lifecycle hook  clear the interval   ngOnDestroy        clearInterval this interval

User · Answer

With rxjs 6 2 2 and Angular 6 1 7  I was getting an      Observable timer is not a function   error  This was resolved by replacing Observable timer with timer   import   timer  Subscription   from  rxjs    private myTimerSub  Subscription       ngOnInit            const ti   timer 2000 1000           this myTimerSub   ti subscribe t   gt                console log  Tick                           ngOnDestroy             this myTimerSub unsubscribe

User · Answer

Found a npm package that makes this easy with RxJS as a service   https   www npmjs com package ng2-simple-timer  You can  subscribe  to an existing timer so you don t create a bazillion timers if you re using it many times in the same component

User · Answer

Another solution is to use TimerObservable  TimerObservable is a subclass of Observable   import  Component  OnInit  OnDestroy  from   angular core   import  Subscription  from  rxjs   import  TimerObservable  from  rxjs observable TimerObservable     Component     selector   app-component     template     tick        export class Component implements OnInit  OnDestroy      private tick  string    private subscription  Subscription     constructor            ngOnInit         let timer   TimerObservable create 2000  1000       this subscription   timer subscribe t   gt          this tick   t                 ngOnDestroy         this subscription unsubscribe            P S   Don t forget to unsubsribe

User · Answer

import  Component  View  OnInit  OnDestroy  from  angular2 core    import   Observable  Subscription   from  rxjs Rx     Component       export class NewContactComponent implements OnInit  OnDestroy        ticks   0      private timer         Subscription object     private sub  Subscription        ngOnInit             this timer   Observable timer 2000 5000              subscribing to a observable returns a subscription object         this sub   this timer subscribe t   gt  this tickerFunc t              tickerFunc tick           console log this           this ticks   tick            ngOnDestroy            console log  Destroy timer               unsubscribe here         this sub unsubscribe

User · Answer

In Addition to all the previous answers  I would do it using RxJS  Observables  please check Observable timer  Here is a sample code  will start after 2 seconds and then ticks every second   import  Component  from  angular2 core   import  Observable  from  rxjs Rx     Component       selector   my-app       template   Ticks  every second      ticks       export class AppComponent     ticks  0    ngOnInit        let timer   Observable timer 2000 1000       timer subscribe t  gt this ticks   t           And here is a working plunker  Update If you want to call a function declared on the AppComponent class  you can do one of the following        Assuming the function you want to call is named func   ngOnInit        let timer   Observable timer 2000 1000       timer subscribe this func       The problem with the above approach is that if you call  this  inside func  it will refer to the subscriber object instead of the AppComponent object which is probably not what you want   However  in the below approach  you create a lambda expression and call the function func inside it  This way  the call to func is still inside the scope of AppComponent  This is the best way to do it in my opinion    ngOnInit        let timer   Observable timer 2000 1000       timer subscribe t  gt            this func t               check this plunker for working code

User · Answer

If you look to run a method on ngOnInit you could do something like this   import this 2 libraries from RXJS   import  Observable  from  rxjs Rx   import  Subscription  from  rxjs     Then declare timer and private subscription  example   timer  Observable timer 1000 1000      1 second for 2 seconds  2000 1000  etc private subscription  Subscription    Last but not least run method when timer stops  ngOnInit       this subscription   this timer subscribe ticks  gt        this populatecombobox       example calling a method that populates a combobox     this subscription unsubscribe       you need to unsubscribe or it will run infinite times           That s all  Angular 5

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