AssetLoader

import AssetLoader from '@bbc/front-end-kit/js/pdf/core/AssetLoader';

Provides an easy API to load all the necessary assets (images and fonts) for PDF creation with PDFKit. The class caches the loaded assets in a static way, sharing the cache across all AssetLoader instances.

Getting started

import AssetLoader from '@bbc/front-end-kit/js/pdf/core/AssetLoader';

const loader = new AssetLoader();

// load fonts and images in parallel
await Promise.all([
    loader.loadFonts([
        { name: 'font-regular', url: 'path/to/font-regular.ttf' },
        { name: 'font-bold',    url: 'path/to/font-bold.ttf' },
    ]),
    loader.loadImages([
        { name: 'logo', url: 'path/to/logo.png' },
    ]),
]);

// retrieve loaded assets (ArrayBuffer)
const fontBuffer  = loader.getFontFile('font-regular');
const imageBuffer = loader.getImageFile('logo');

API

constructor()

Initialises the AssetLoader instance with empty _fonts and _images arrays.

Methods

getFont(name)

Returns the font definition object for the given name.

Parameters

• name (string): The registered font name.

Returns

object — the font definition { name, url, file, isLoaded, error }.

getFontFile(name)

Returns the loaded file data for the given font.

Parameters

• name (string): The registered font name.

Returns

ArrayBuffer — the raw font file data, ready to pass to PDFKit's .font() method.

loadFonts(fontsData)

Fetches all listed fonts and stores them in the instance cache. Already-loading or already-loaded entries are reused from the static FONT_CACHE.

Parameters

• fontsData (object[]): Array of font definition objects:
  • name (string): Key under which the asset is stored.
  • url (string): URL to the font file.

Returns

Promise — resolves when all fonts are loaded.

getImage(name)

Returns the image definition object for the given name.

Parameters

• name (string): The registered image name.

Returns

object — the image definition { name, url, file, isLoaded, error }.

getImageFile(name)

Returns the loaded file data for the given image.

Parameters

• name (string): The registered image name.

Returns

ArrayBuffer — the raw image file data.

loadImages(imagesData)

Fetches all listed images and stores them in the instance cache. Already-loading or already-loaded entries are reused from the static IMAGE_CACHE.

Parameters

• imagesData (object[]): Array of image definition objects:
  • name (string): Key under which the asset is stored.
  • url (string): URL to the image file.

Returns

Promise — resolves when all images are loaded.

Private properties

Exported utility functions

These are also exported as named exports for advanced use:

getDefinitionFromCache(cache, url)

Looks up a definition by URL in a static cache array. Returns a resolving Promise if already loaded, the in-flight Promise if still loading, or undefined if not found.

createDefinition(data, localCache, cache)

Creates a new definition object { file, isLoaded, error, ...data } and pushes it to both the local instance array and the static cache.

loadData(definition)

Fetches definition.url via fetch, stores the resolved ArrayBuffer in definition.file, sets definition.isLoaded = true, and returns the Promise.