Angular 2, can Http.get ignore 404

Question

I need to the use the HTTP library to check for the existence of a file on the server. It's pretty simple, all I am doing is calling the following code:

private serverHeadRequest(): Observable<any> {
        return this.http.head("theFileName.xxx")
            .map(this.isResponseOkCallBack)
            .catch(this.handleError);
    }

    private isResponseOkCallBack(res: Response) {
        switch (res.status) {
            case 404:
                return false;
            case 200:
                return true;
            default:
                return false;
        }
    }


    private handleError(error: any) {
        let errMsg = (error.message) ? error.message :
            error.status ? `${error.status} - ${error.statusText}` : 'Server error';
        console.error(errMsg); // log to console instead
        return Observable.throw(errMsg);
    }

If the response is a 200 then the code works well. However I would like to simply return false on any other sort of response code.

I tried this as an alternative error handler which I thought would simply return false if there was an error however this didn't work.

private handleError(error: any) {
        return Observable.create()
             .map({
                 return false;
              });
    }

How can I get this working? Is there a way to ignore certain status codes?

Answer 1

Try think you can handle error like this:

// import 'rxjs/add/observable/of'

handleError() {
  return Observable.of(false);
}

Also, note that in case of error, browser will still print HEAD <url> 404 (Not Found) in console. You should not worry about this, most importantly that you handle it properly (but returning false).

Answer 2

When there was an error (which is thrown on most non-2xx responses), isResponseOkCallBack won't be called, because it jumps right into the .catch() block.

Try mapping all successful requests to true and any errors to false.

this.http.head("theFileName.xxx")
            .map(() => true) // or .map(res => (res.status === 200)) 
            .catch(() => Observable.of(false));