How can I fix this error ? days: NaN yearsNaN monthsNaN weeksNaN daysNaN minutesNaN seconds

Issue

I'm working on an ionic project, and have this error. I have have a button , I want print date that user select

My code

age.component.ts

import { Component, OnInit } from '@angular/core';
import * as moment from'moment';
@Component({
 .....
})
export class AgeComponent implements OnInit {
dob:any = '' ;
myDate = {
  years: 0,
  months:0,
  weeks:0,
  days:0,
  minutes:0,
  seconds:0,
}
  constructor() { }
  calculateAge(){
      let todaysDate = moment(new Date());
      let dob = moment( new Date(this.dob) );
      let duration = moment.duration(todaysDate.diff(dob));
      this.myDate.years = duration.years();
      this.myDate.months = Math.floor(duration.asMonths());
      this.myDate.weeks = Math.floor(duration.asWeeks());
      this.myDate.days = Math.floor(duration.asDays());
      this.myDate.minutes = Math.floor(duration.asMinutes());
      this.myDate.seconds = Math.floor(duration.asSeconds());
  }
    }

And here is my age.component.html code

<ion-datetime class="datetime" [(ngModel)]="dob" pickerFormat="MMM DD YYYY" 
displayFormat="MMM DD, YYYY" min="1950-01-01" max="2050-01-01"></ion-datetime>
<ion-button (click)="calculateAge()" >Calculate</ion-button>
  <span>{{myDate.years}} years</span>
  <span>{{myDate.months}} months</span>
  <span>{{myDate.weeks}} weeks</span>
  <span>{{myDate.days}} days</span>
  <span>{{myDate.minutes}} minutes</span>
  <span>{{myDate.seconds}} seconds</span>

Solution

The NaN error only happens when you not select any date from ion-datetime. to solve that problem you can simply add condition in your variable let dob to let dob = moment( new Date(this.dob ? this.dob : todaysDate));

TS

calculateAge(){
      let todaysDate = moment(new Date());
      let dob = moment( new Date(this.dob ? this.dob : todaysDate)); <-- add condition here
      let duration = moment.duration(todaysDate.diff(dob));
      this.myDate.years = duration.years();
      this.myDate.months = Math.floor(duration.asMonths());
      this.myDate.weeks = Math.floor(duration.asWeeks());
      this.myDate.days = Math.floor(duration.asDays());
      this.myDate.minutes = Math.floor(duration.asMinutes());
      this.myDate.seconds = Math.floor(duration.asSeconds());
}

here's the sample

Answered By - Nicho