Angular: Prevent route change if any changes made in the view

Question

If I have a form in a view (Angular). When user tries to navigate away from there, and I want a confirmation message to appear. How can I do that?

Answer 1

You can implement canDeactivate using typescript like

import { Injectable } from '@angular/core';
import { CanDeactivate } from '@angular/router';
import { ViewthatyouwantGuard } from './path to your view';

@Injectable()
export class ConfirmDeactivateGuard implements CanDeactivate {
    
    canDeactivate(target: ViewthatyouwantGuard) {
        if (target.hasChanges) {
            return window.confirm('Do you really want to cancel?');
        }
        return true;
    }

}

// hasChanges - function in 'ViewthatyouwantGuard' which will return true or false based on unsaved changes

// And in your routing file provide root like 
{path:'rootPath/', component: ViewthatyouwantGuard, canDeactivate:[ConfirmDeactivateGuard]},

// Last but not least, also this guard needs to be registered accordingly:
@NgModule({
    ...
    providers: [
        ...
        ConfirmDeactivateGuard
    ]
 })
 export class AppModule {}

Source: https://blog.thoughtram.io/angular/2016/07/18/guards-in-angular-2.html