Typescript instanceof - Cannot find name

Question

I have a problem with Typescript compilation. This code returns the error:

error TS2304: Cannot find name 'NavigationEnd'.

How can I make the compiler know about NavigationEnd type? NavigationEnd is angular2 router event type.

this.router.events.subscribe((e) => {e instanceof NavigationEnd ? 
console.log('NavigationEnd'):console.log('Not NavigationEnd')});

I`m using IDE PHPStorm.

Weird. Everything else auto imports with VS Code's intellisense, but NavigationEnd won't? Things like ActivatedRoute and Router were imported into @angular/router, but I had to type NavigationEnd in manually. — JimmyTheCode
– JimmyTheCode, Commented Apr 2, 2023 at 16:29

Günter Zöchbauer · Accepted Answer · 2016-07-04 08:30:17Z

26

Seems you're missing an import

import { Router, NavigationEnd } from '@angular/router'

answered Jul 4, 2016 at 8:30

Günter Zöchbauer

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3 Comments

Aluan Haddad Over a year ago

Why is Angular2 encourage/forcing this anti-pattern on developers? What value is there in using instanceof to test an Event type?

Günter Zöchbauer Over a year ago

I don't use TS myself (only Dart) and in Dart and other languages I know this is no antipattern. Perhaps filter like shown in stackoverflow.com/questions/33520043/… is a bit of an improvment.

Aluan Haddad Over a year ago

In JavaScript it is a very confusing pattern because it looks like it does in other languages, but it doesn't even have the same kinds of operands. Java : x instanceof T -> x is a value and T is a type; JavaScript : x instanceof T -> x is a value and T is a value; It also couples you to an implementation detail, why should I care that it has a specific prototype?

Dylan Meeus · Accepted Answer · 2016-07-04 08:24:03Z

4

I did a small test and it seems that you might have forgotten to include "NavigationEnd" as an import to your project. (Like günter hinted at in the comments)

import { NavigationEnd } from '@angular/router';

After including this, TypeScript no longer complained about it being missing ;-)

answered Jul 4, 2016 at 8:24

Dylan Meeus

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