Comparing 2 strings from HTML file - Angular - html

Question

I am using angular 7 and I would like to know how to compare two strings. In this case, each of my strings simulates one date, let's say "2019-12-26" and "2018-12-26".
In Javascript is pretty simple to compare them since I just need to use the operators:
console.log(today > "2018-12-06");
It is working how I supposed it was gonna work. It basically returns true. Nevertheless, I am trying to do exactly the same from my HTML file
<div *ngIf="today > example.endDate">
being today and 'example.endDate' two strings containing exactly the same strings that I used for the Javascript example, but it does not show any of them.
Is there any other way to make this comparison?
Regards,
Mario
UPDATE
I have had a second look at the problem and it seems that the comparison is not a problem, but the way of getting the variable is.
I get a variable in ngOnInit().
ngOnInit() {
this.getCurrentDate();
}
//Get current date
getCurrentDate() {
let aux = new Date();
//2 characteres
let dd = String(aux.getDate()).padStart(2, "0");
let mm = String(aux.getMonth() + 1).padStart(2, "0"); //January is 0!
let yyyy = aux.getFullYear();
let today = yyyy + "-" + mm + "-" + dd;
let other = "2019-01-31";
}
The problem is that I use this variable directly in my HTML how I previously showed. The error I get is the following:
ERROR Error: ExpressionChangedAfterItHasBeenCheckedError: Expression
has changed after it was checked. Previous value: 'ngIf: undefined'.
Current value: 'ngIf: true'.
So the problem is that I am using a variable in the HTML file before getting the value. Or at least it is what I understand
To check this error I have created a Stackblitz representation. On it, I have created two examples:
Variables not on ngOnInit()
Variables in ngOnInit()
https://stackblitz.com/edit/angular-jjgsmq?file=src%2Fapp%2Fhello.component.ts

Answer 1

the most simple solution is just to
and are you sure that ngOnInit is the right LifeCycle hook for you?
I would try ngAfterContentInit() if the component is "heavy" to render other wise ngAfterViewInit() would have been my choice
<div *ngIf="IsTodayBigger()">
ngOnInit() {
this.getCurrentDate();
}
IsTodayBigger(): boolean {
today=this.getCurrentDate()
exampleEndDate= example.endDate;//use binding or ViewChild if needed
return today&&exampleEndDate&& today> example.endDate
}
//Get current date
getCurrentDate() {
let aux = new Date();
//2 characteres
let dd = String(aux.getDate()).padStart(2, "0");
let mm = String(aux.getMonth() + 1).padStart(2, "0"); //January is 0!
let yyyy = aux.getFullYear();
today = yyyy + "-" + mm + "-" + dd;
let other = "2019-01-31";
}