ng-defer-load
ng-defer-load is an Angular directive to load elements lazily.
It uses Intersection Observer API to check if an element is in viewport and falls back to scroll detection mechanism for unsupported browsers.
Installation
Using npm:
$ npm i @trademe/ng-defer-load
Usage
-
Import
DeferLoadModule
into the module corresponding to your component -
Use the directive with the element you wish to lazy load
<div
(deferLoad)="showMyElement=true">
<my-element
*ngIf=showMyElement>
...
</my-element>
</div>
Note: You might want to have a loading state for your element with approximately same height as the element.
Server Side Rendering
ng-defer-load
supports Server Side Rendering from version 1.1.0
It loads the element on the server by default supporting Search Engine Optimization. If you do not want to pre-render the element in server, you can set preRender
to false on the element as below:
<div
[preRender]="false"
(deferLoad)="showMyElement=true">
<my-element
*ngIf=showMyElement>
...
</my-element>
</div>
Fall back support
ng-defer-load
supports a fall back in browsers or devices (like older iPhones) that do not support the IntersectionObserver API. This uses the scroll position and the element's offset. This is enabled by default.
If you do not want to allow this fallback, and would prefer the browser to just render the element regardless, you can set fallbackEnabled
to false on the element as below:
<div
[fallbackEnabled]="false"
(deferLoad)="showMyElement=true">
<my-element
*ngIf=showMyElement>
...
</my-element>
</div>
Demo
Demo of ng-defer-load in use is available here.
License
Released under the MIT license.
Release notes
v1.0.1 - Initial version
v1.1.0 - Supports Universal - Server Side Rendering
v2.0.0 - Supports Angular 6
v3.0.0 - Supports Angular 7
v3.1.0 - Made it possible to switch off scroll fallback
v8.0.0 - Supports Angular 8/9
v8.1.0 - Supports more package formats (using ng-packagr)
v8.2.0 - Added option to remove listeners after load
v8.2.1 - Fix for IE11 and older browsers
v8.2.2 - Updated dependencies due to security advisories
v14.0.0 - Supports Angular 12+ (targeting Angular 14) with partial Ivy builds. Additionally, drops support for IE11.