ngx-lottie

A minimal customizable performance-stable Angular component for rendering After Effects animations. Compatible with Angular 9+.

Table of contents

• Features
• Quick example
• Installation
• Usage
• Updating animation
• Listening to lottie-web events
• Caching
• API
• Reducing lottie-web bundle size
• Optimizations
• Server side rendering
• Potential pitfalls

Features

• rich: ngx-lottie provides more opportunities to work with API exposed by Lottie
• strict: all types of objects and events are available to you
• performant: the lottie-web library can be loaded synchronously or on-demand

Quick example

<ng-lottie
  width="600px"
  height="500px"
  containerClass="moving-box another-class"
  [styles]="styles"
  [options]="options"
  (animationCreated)="animationCreated($event)"
  (configReady)="configReady()"
  (dataReady)="dataReady()"
  (domLoaded)="domLoaded()"
  (enterFrame)="enterFrame($event)"
  (segmentStart)="segmentStart($event)"
  (complete)="complete($event)"
  (loopComplete)="loopComplete($event)"
  (destroy)="destroy($event)"
  (error)="error($event)"
></ng-lottie>

Installation

To install ngx-lottie, run the following command:

npm i lottie-web ngx-lottie
# Or if you use yarn
yarn add lottie-web ngx-lottie

Usage

First, import the LottieModule into the AppModule:

import { NgModule } from '@angular/core';
import { LottieModule } from 'ngx-lottie';
import player from 'lottie-web';

// Note we need a separate function as it's required
// by the AOT compiler.
export function playerFactory() {
  return player;
}

@NgModule({
  imports: [LottieModule.forRoot({ player: playerFactory })],
})
export class AppModule {}

The lottie-web library can be loaded on demand using dynamic import. Webpack will load this library only when your animation gets rendered for the first time. Given the following code:

import { NgModule } from '@angular/core';
import { LottieModule } from 'ngx-lottie';

export function playerFactory() {
  return import(/* webpackChunkName: 'lottie-web' */ 'lottie-web');
}

@NgModule({
  imports: [LottieModule.forRoot({ player: playerFactory })],
})
export class AppModule {}

Now you can use the ng-lottie component and provide your custom options via the options binding.

import { Component } from '@angular/core';
import { AnimationItem } from 'lottie-web';
import { AnimationOptions } from 'ngx-lottie';

@Component({
  selector: 'app-root',
  template: `
    <ng-lottie [options]="options" (animationCreated)="animationCreated($event)"></ng-lottie>
  `,
})
export class AppComponent {
  options: AnimationOptions = {
    path: '/assets/animation.json',
  };

  animationCreated(animationItem: AnimationItem): void {
    console.log(animationItem);
  }
}

Also, it's possible to use the lottie directive if you'd like to provide your custom container and manage it:

import { Component } from '@angular/core';
import { AnimationItem } from 'lottie-web';
import { AnimationOptions } from 'ngx-lottie';

@Component({
  selector: 'app-root',
  template: `
    <main lottie [options]="options" (animationCreated)="animationCreated($event)"></main>
  `,
})
export class AppComponent {
  options: AnimationOptions = {
    path: '/assets/animation.json',
  };

  animationCreated(animationItem: AnimationItem): void {
    console.log(animationItem);
  }
}

Note that you will need to import the LottieModule into other modules as it exports the ng-lottie component, and the lottie directive. forRoot has to be called only once!

Updating animation

If you want to update the animation dynamically then you have to update the animation options immutably. Let's look at the following example:

import { Component } from '@angular/core';
import { AnimationItem } from 'lottie-web';
import { AnimationOptions } from 'ngx-lottie';

@Component({
  selector: 'app-root',
  template: `
    <ng-lottie [options]="options" (animationCreated)="animationCreated($event)"></ng-lottie>
    <button (click)="updateAnimation()">Update animation</button>
  `,
})
export class AppComponent {
  options: AnimationOptions = {
    path: '/assets/animation.json',
  };

  animationCreated(animationItem: AnimationItem): void {
    console.log(animationItem);
  }

  updateAnimation(): void {
    // ⚠️⚠️ Don't do this!
    this.options.path = '/assets/new-animation.json';

    // ✔️✔️ Update `options` in this way
    this.options = {
      ...this.options, // In case you have other properties that you want to copy
      path: '/assets/new-animation.json',
    };
  }
}

If you want to update options relying on a response from the server, then you'll have to call markForCheck to make sure that Angular will run the change detection if ng-lottie is inside a ChangeDetectionStrategy.OnPush component:

import { Component, ChangeDetectionStrategy, ChangeDetectorRef } from '@angular/core';
import { AnimationItem } from 'lottie-web';
import { AnimationOptions } from 'ngx-lottie';

@Component({
  selector: 'app-root',
  template: `
    <ng-lottie [options]="options" (animationCreated)="animationCreated($event)"></ng-lottie>
    <button (click)="updateAnimation()">Update animation</button>
  `,
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class AppComponent {
  options: AnimationOptions = {
    path: '/assets/animation.json',
  };

  constructor(private ref: ChangeDetectorRef, private animationService: AnimationService) {}

  animationCreated(animationItem: AnimationItem): void {
    console.log(animationItem);
  }

  updateAnimation(): void {
    this.animationService.loadAnimationOptions().subscribe(options => {
      this.options = options;
      this.ref.markForCheck();
    });
  }
}

You can also store options in BehaviorSubject and bind them via the async pipe in a template:

@Component({
  selector: 'app-root',
  template: `
    <ng-lottie
      [options]="options$ | async"
      (animationCreated)="animationCreated($event)"
    ></ng-lottie>

    <button (click)="updateAnimation()">Update animation</button>
  `,
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class AppComponent {
  options$ = new BehaviorSubject<AnimationOptions>({
    path: '/assets/animation.json',
  });

  constructor(private ref: ChangeDetectorRef, private animationService: AnimationService) {}

  animationCreated(animationItem: AnimationItem): void {
    console.log(animationItem);
  }

  updateAnimation(): void {
    this.animationService.loadAnimationOptions().subscribe(options => {
      this.options$.next(options);
    });
  }
}

Listening to lottie-web events

The ng-lottie adds event listeners to those events that are listened outside. This means that if you've got the following code:

<ng-lottie (loopComplete)="onLoopComplete()"></ng-lottie>

In the above example, the ng-lottie will only listen to the loopComplete event on the AnimationItem under the hood. One important note that all events are handled outside of the Angular zone:

ngZone.runOutsideAngular(() => {
  animationItem.addEventListener('loopComplete', () => {});
});

I made such a design decision because animation items can emit hundreds and thousands of events every second. The lottie-web emits some events asynchronously by wrapping them into setTimeout internally. If thousands of events occur during a single second, then Angular will run change detection a thousand times, drastically decreasing performance.

Therefore, event handlers will be called outside of the Angular zone:

import { Component, ChangeDetectionStrategy, NgZone } from '@angular/core';
import { AnimationOptions } from 'ngx-lottie';

@Component({
  selector: 'app-root',
  template: ` <ng-lottie [options]="options" (loopComplete)="onLoopComplete()"></ng-lottie> `,
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class AppComponent {
  options: AnimationOptions = {
    path: '/assets/animation.json',
  };

  onLoopComplete(): void {
    NgZone.assertNotInAngularZone();
    console.log(NgZone.isInAngularZone()); // false
  }
}

Therefore you need:

• either call NgZone.run()
• either call change detection manually via ChangeDetectorRef.detectChanges()
• either mark component to be checked via ChangeDetectorRef.markForCheck()

import { Component, ChangeDetectionStrategy, NgZone, ChangeDetectorRef } from '@angular/core';
import { AnimationOptions } from 'ngx-lottie';

// Angular 9+
import { ɵdetectChanges as detectChanges, ɵmarkDirty as markDirty } from '@angular/core';

@Component({
  selector: 'app-root',
  template: `
    <ng-lottie [options]="options" (loopComplete)="onLoopComplete()"></ng-lottie>
    <p>On loop complete called times = {{ onLoopCompleteCalledTimes }}</p>
  `,
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class AppComponent {
  options: AnimationOptions = {
    path: '/assets/animation.json',
  };

  onLoopCompleteCalledTimes = 0;

  constructor(private ngZone: NgZone, private ref: ChangeDetectorRef) {}

  onLoopComplete(): void {
    // * first option via `NgZone.run()`
    this.ngZone.run(() => {
      this.onLoopCompleteCalledTimes++;
    });

    // * second option via `ChangeDetectorRef.detectChanges()`
    this.onLoopCompleteCalledTimes++;
    this.ref.detectChanges();
    // Angular 9+
    detectChanges(this);

    // * third option via `ChangeDetectorRef.markForCheck()`
    this.onLoopCompleteCalledTimes++;
    this.ref.markForCheck();
    // Angular 9+
    markDirty(this);
  }
}

Caching

The lottie-web will load your JSON file whenever animation is created. When importing the LottieModule into the root module, you can also import the LottieCacheModule:

import { NgModule } from '@angular/core';
import { LottieModule, LottieCacheModule } from 'ngx-lottie';

export function playerFactory() {
  return import(/* webpackChunkName: 'lottie-web' */ 'lottie-web');
}

@NgModule({
  imports: [LottieModule.forRoot({ player: playerFactory }), LottieCacheModule.forRoot()],
})
export class AppModule {}

This will enable cache under the hood. Since the cache is enabled, ngx-lottie will load your JSON file only once.

API

Bindings

The ng-lottie component supports the following bindings:

@Component({
  selector: 'app-root',
  template: `
    <ng-lottie
      width="500px"
      height="600px"
      containerClass="moving-box"
      [styles]="styles"
      [options]="options"
    ></ng-lottie>
  `,
})
export class AppComponent {
  options: AnimationOptions = {
    path: '/assets/animation.json',
  };

  styles: Partial<CSSStyleDeclaration> = {
    maxWidth: '500px',
    margin: '0 auto',
  };
}

• options: AnimationOptions options used by AnimationItem
• width?: string container element width in pixels. Bound to [style.width]. You can provide any CSS unit, e.g. 100em
• height?: string container element height in pixels. Bound to [style.height]. You can provide any CSS unit, e.g. 100em
• styles?: Partial<CSSStyleDeclaration> custom styles object. Bound to [ngStyle]
• containerClass?: string custom container class(es). Bound to [ngClass].

The lottie directive supports only options binding.

Events

@Output()	Type	Required	Description
animationCreated	AnimationItem	optional	Dispatched after the lottie successfully creates animation
configReady	void	optional	Dispatched after the needed renderer is configured
dataReady	void	optional	Dispatched when all parts of the animation have been loaded
domLoaded	void	optional	Dispatched when elements have been added to the DOM
enterFrame	BMEnterFrameEvent	optional	Dispatched after entering the new frame
segmentStart	BMSegmentStartEvent	optional	Dispatched when the new segment is adjusted
loopComplete	BMCompleteLoopEvent	optional	Dispatched after completing frame loop
complete	BMCompleteEvent	optional	Dispatched after completing the last frame
destroy	BMDestroyEvent	optional	Dispatched in the ngOnDestroy hook of the service that manages lottie's events, it's useful for releasing resources
error	BMRenderFrameErrorEvent OR BMConfigErrorEvent	optional	Dispatched if the lottie player could not render some frame or parse the config

Reducing lottie-web bundle size

The size of the lottie-web library is quite large. Because when we write this:

import player from 'lottie-web';

export function playerFactory() {
  return player;
}

// Or if you load `lottie-web` on demand
export function playerFactory() {
  return import(/* webpackChunkName: 'lottie-web' */ 'lottie-web');
}

It bundles all 3 renderers: CanvasRenderer, SVGRenderer and HybridRenderer. The SVGRenderer is used by default. If you don't care which renderer is used and never provide the renderer option, you might want to exclude CanvasRenderer and HybridRenderer. To do this, just import the lottie_svg file that is inside the lottie-web/build/player folder:

import player from 'lottie-web/build/player/lottie_svg';

export function playerFactory() {
  return player;
}

// Or if you load `lottie-web` on demand
export function playerFactory() {
  return import(/* webpackChunkName: 'lottie-web' */ 'lottie-web/build/player/lottie_svg');
}

Its minified size is 198 KiB.

You can also use the lottie-web light version. As Hernan Torrisi (author of lottie-web) explains:

It should work fine, but animations won't render correctly if they have expressions or effects.

The light version can be imported using the following code:

import player from 'lottie-web/build/player/lottie_light';

export function playerFactory() {
  return player;
}

// Or if you load `lottie-web` on demand
export function playerFactory() {
  return import(/* webpackChunkName: 'lottie-web' */ 'lottie-web/build/player/lottie_light');
}

Its minified size is 148 KiB. Use this at your own risk because I can't know if your animations contain expressions or effects.

Optimizations

The ng-lottie component is marked with the OnPush change detection strategy. This means Angular will not check it in any phase of the change detection mechanism until you change the reference to some binding. For example, if you use an svg renderer and there are a lot of DOM elements projected — you would like to avoid checking this component, as it's not necessary.

The ngx-lottie listens to AnimationItem events outside of the Angular zone. It would be best if you didn't worry that animation events will cause change detection every ms.

But be careful! Always wrap any calls to AnimationItem methods in runOutsideAngular. See the below code:

import { Component, NgZone } from '@angular/core';
import { AnimationItem } from 'lottie-web';
import { AnimationOptions } from 'ngx-lottie';

@Component({
  selector: 'app-root',
  template: `
    <ng-lottie [options]="options" (animationCreated)="animationCreated($event)"></ng-lottie>

    <button (click)="stop()">Stop</button>
    <button (click)="play()">Play</button>
  `,
})
export class AppComponent {
  options: AnimationOptions = {
    path: '/assets/animation.json',
  };

  private animationItem: AnimationItem;

  constructor(private ngZone: NgZone) {}

  animationCreated(animationItem: AnimationItem): void {
    this.animationItem = animationItem;
  }

  stop(): void {
    this.ngZone.runOutsideAngular(() => {
      this.animationItem.stop();
    });
  }

  play(): void {
    this.ngZone.runOutsideAngular(() => {
      this.animationItem.play();
    });
  }
}

Server-side rendering

By default, lottie-web will load your JSON file with animation data every time you create an animation. You may have some problems with the connection, so there may be some delay or even timeout. It's worth loading animation data only once and cache it on the client-side, so every time you create an animation — ngx-lottie will retrieve the animation data from the cache.

ngx-lottie/server package gives you the opportunity to preload animation data and cache it using TransferState.

How2?

TL;DR - see the integration folder.

Import the LottieServerModule into your AppServerModule:

import { NgModule } from '@angular/core';
import { ServerModule, ServerTransferStateModule } from '@angular/platform-server';
import { LottieServerModule } from 'ngx-lottie/server';

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

@NgModule({
  imports: [
    // `AppModule` first as you know
    AppModule,
    ServerModule,
    ServerTransferStateModule,
    LottieServerModule.forRoot({
      preloadAnimations: {
        folder: 'dist/browser/assets',
        animations: ['data.json'],
      },
    }),
  ],
  bootstrap: [AppComponent],
})
export class AppServerModule {}

Don't forget to import the BrowserTransferStateModule into your AppModule. Let's look at these options. animations is an array of JSON files that contain animation data that Node.js should read on the server-side, cache and transfer to the client. folder is a path where your JSON files are located, but you should use it properly, this path is joined with the process.cwd(). Assume such a project structure:

— dist (here you store your output artifacts)
  — browser
    — assets
    — index.html
    — main.hash.js
  - server
    - main.js
— src (here is your app)
— angular.json
— package.json
— webpack.config.js

If you start a server from the root folder like node dist/server/main, thus the folder property should equal dist/browser/assets.

You now can inject the LottieTransferState in your components from the ngx-lottie package. It's tree-shakable by default and won't get bundled until you inject it anywhere:

import { Component } from '@angular/core';
import { AnimationOptions, LottieTransferState } from 'ngx-lottie';

@Component({
  selector: 'app-root',
  template: ` <ng-lottie [options]="options"></ng-lottie> `,
})
export class AppComponent {
  options: AnimationOptions = {
    animationData: this.lottieTransferState.get('data.json'),
  };

  constructor(private lottieTransferState: LottieTransferState) {}
}

Notice, data.json is a filename that you pass to the preloadAnimations.animations property. Finally change this:

platformBrowserDynamic().bootstrapModule(AppModule);

To this:

document.addEventListener('DOMContentLoaded', () => {
  platformBrowserDynamic().bootstrapModule(AppModule);
});

Potential pitfalls

There is only one potential pitfall associated with animations in the Safari browser. Also, this known issue is in the lottie-web library itself. Library consumers have been trying to resolve that issue using different solutions. The only solution that helped most people was installing the latest version of the lottie-web.