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ERROR ReferenceError: localStorage is not defined in Angular 17/18

The error ReferenceError: localStorage is not defined occurs in Angular projects when localStorage is accessed in an environment where it is not available, such as on the server side during server-side rendering (SSR) using Angular Universal. The localStorage API is part of the browser's window object, and it is unavailable in non-browser environments.

To fix this error in your Angular 18 project, you can use the following approaches:


1. Check if localStorage Exists

Ensure localStorage is accessed only in the browser. Modify your service or component code to check for its availability before using it.


if (typeof window !== 'undefined' && window.localStorage) { // Access localStorage here localStorage.setItem('key', 'value'); } else { console.warn('localStorage is not available.'); }

2. Use Angular's Dependency Injection for Platform Check

Use Angular's PLATFORM_ID to check whether the code is running in a browser or on the server.

Example:


import { Injectable, Inject, PLATFORM_ID } from '@angular/core'; import { isPlatformBrowser } from '@angular/common'; @Injectable({ providedIn: 'root', }) export class StorageService { private isBrowser: boolean; constructor(@Inject(PLATFORM_ID) private platformId: object) { this.isBrowser = isPlatformBrowser(platformId); } setItem(key: string, value: string): void { if (this.isBrowser) { localStorage.setItem(key, value); } else { console.warn('localStorage is not available on the server.'); } } getItem(key: string): string | null { if (this.isBrowser) { return localStorage.getItem(key); } console.warn('localStorage is not available on the server.'); return null; } }

3. Provide a Fallback for Non-Browser Environments

If the application requires data persistence in both client and server environments, use an alternative to localStorage, such as an in-memory store.

Example:


@Injectable({ providedIn: 'root', }) export class StorageService { private memoryStorage: { [key: string]: string } = {}; setItem(key: string, value: string): void { if (typeof window !== 'undefined' && window.localStorage) { localStorage.setItem(key, value); } else { this.memoryStorage[key] = value; } } getItem(key: string): string | null { if (typeof window !== 'undefined' && window.localStorage) { return localStorage.getItem(key); } return this.memoryStorage[key] || null; } }

4. Handle SSR-Specific Code in the Angular Universal App

If using Angular Universal, make sure localStorage calls are wrapped and executed only in the browser.

Example in Component:


import { Component, Inject, PLATFORM_ID } from '@angular/core'; import { isPlatformBrowser } from '@angular/common'; @Component({ selector: 'app-root', templateUrl: './app.component.html', }) export class AppComponent { constructor(@Inject(PLATFORM_ID) private platformId: object) { if (isPlatformBrowser(this.platformId)) { // Access localStorage safely localStorage.setItem('key', 'value'); } } }

These approaches will ensure localStorage is used only in environments where it is available, resolving the error in your Angular 18 project. Let me know if you need further guidance!

By Anil Singh | Rating of this article (*****)

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