[html] How to declare a variable in a template in Angular

If you need autocomplete support from within in your templates from the Angular Language Service:

Synchronous:

myVar = { hello: '' };

<ng-container *ngIf="myVar; let var;">
  {{var.hello}}
</ng-container>

Using async pipe:

myVar$ = of({ hello: '' });

<ng-container *ngIf="myVar$ | async; let var;">
  {{var.hello}}
</ng-container>