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NgxMutationObserver

Angular 19.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.

NgxMutationObserverDirective

Emits MutationRecord[] when a mutation is detected.

<div (onMutation)="handleMutation($event)"></div>

Configuration is allowed through the mutationConfig directive. When not specified, this defaults to {attributes: true, characterData: true, childList: true }. You are allowed to specify anything allowed in the interface. For instance, if you only care about the size of an element changing, you would only watch its attributes.

<div (onMutation)="attributesChanged($event)" [mutationConfig]="{attributes: true}"></div>

License

This project is licensed under an MIT license.