How to get the previous page URL in angular 5

Question

I'm working with Angular 5 app and I need to know how to get the last URL to place it as a link to my back button. I found this location.back() but what I need the last url as a string. How could I get the string that generates location.back()?

Many Thanks!

Answer 1

Angular 6 updated code for getting previous url as string.

import { Component, OnInit } from '@angular/core';
import { Router, RoutesRecognized } from '@angular/router';
import { filter, pairwise } from 'rxjs/operators';


export class AppComponent implements OnInit {

    constructor (
        public router: Router
    ) {
    }

    ngOnInit() {
        this.router.events
            .pipe(filter((e: any) => e instanceof RoutesRecognized),
                pairwise()
            ).subscribe((e: any) => {
                console.log(e[0].urlAfterRedirects); // previous url
            });
    }

Answer 2

In the browser environment, location.back() is wrapper around the window.history object (for a partial path through the source, see here, here, here and here).

The contents within the History object are purposefully not accessible.

From the HTML History interface documention:

The actual entries are not accessible from script.

From MDN the window.history object documentation:

For security reasons the History object doesn't allow the non-privileged code to access the URLs of other pages in the session history, but it does allow it to navigate the session history.

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As to an alternate approach, this answer provides a technique for listening for the last 2 NavigationEnd events.