Update ngModel if it's not null angular 5

Question

I'd like to update [(ngModel)] using onclickevent only if the value is not null. Here's what i tried

click event method:

  setBiometricsStartTime() {
     let startTimeStore = new Date();
     if(this.startTime == undefined) 
     {
         this.startTime = new Date();
     }
     else 
     {
        this.startTime = startTimeStore;
     }
  }

html code:

[...]
   <mat-expansion-panel
    (opened)="personalDetailsOpenState = true" (closed)="personalDetailsOpenState = false" (click)="setBiometricsEndTime()
   </mat-expansion-panel>
[...]

Unfortunately, the model value is being generated on every click event.

Answer 1

You are setting it in else condition, try

if(!this.startTime || this.startTime==undefined) 
 {
     this.startTime = new Date();
 }