TypeScript is not type safe

Let’s say we have an API that return true or false ( TILT – Things I learned Today – http://tiltwebapp.azurewebsites.net/  – returns true if I have learned something today )

What is wrong with this code:

public HasTILTToday():Observable<boolean>{

if(!this.wasLoggedIn)return of(false);

return this.http.get<string>(this.baseUrl+’TILT/HasTILTToday’, {

headers: new HttpHeaders(

        {

‘Authorization’: ‘CustomBearer ‘ + this.jwt,

‘Content-Type’: ‘application/json’

        }),       

responseType: ‘text’ as ‘json’})

    ;

  }

…

…

….

Answer : When you subscribe,even the variable is boolean, when you go with typeof is a string ( that contains “true” or “false” ). And this, when you use  a *ngIf =”the bool” – it will have undexpected behaviours.

Solution? The rxjs pipe

public HasTILTToday():Observable<boolean>{

if(!this.wasLoggedIn)return of(false);

return this.http.get<string>(this.baseUrl+’TILT/HasTILTToday’, {

headers: new HttpHeaders(

        {

‘Authorization’: ‘CustomBearer ‘ + this.jwt,

‘Content-Type’: ‘application/json’

        }),       

responseType: ‘text’ as ‘json’})

      .pipe(

map(it=>it===’true’)

      );

  }