NgxMutationObserver

Angular 21.x library to monitor changes to elements. Uses MutationObserver to do the work.

If you're only looking for a way to see if elements are visible, I suggest checking out ngx-visibility instead. This doesn't notice everything - for instance, an element whose width is set to "50%" will not report a mutation when the window is resized or when a scrollbar is visible. Instead, a mutation is reported when the width is changed from "50%" to "75%" or to "128px".

If you only care about when elements are resized, including resize events due to browser window size changing, look at ngx-resize-observer.

Demonstration

There's a live demo over at CodeSandbox.io.

Installation

Install like other Angular libraries. First run a command to download the module.

npm install ngx-mutation-observer

Next, add the module to your project.

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';

// Import the module
import { NgxMutationObserverModule } from 'ngx-mutation-observer';

import { AppComponent } from './app.component';

@NgModule({
declarations: [AppComponent, ItemComponent],

// Include the module.
imports: [BrowserModule, FormsModule, NgxMutationObserverModule],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule {}

Finally, you leverage the service directly or use some directives for common uses.