A promisified FileReader for browsers

A promisified FileReader implementation very similar to the browser's FileReader API, with a few differences:

• the File or Blob instance is given at construction time;
• all readAs... methods don't take a Blob or File instance as first argument anymore;
• all readAs... methods return a Promise that can be awaited;
• reading in chunks is easy as:
  • you just need to await the next chunk (no event / callback API anymore);
  • the current reading position is automatically tracked.

Usage

import { FileReader } from '@tanker/file-reader';

// Retrieve a file or blob somehow
const file = new File(
  ['The quick brown fox jumps over the lazy dog'],
  'fox.txt',
  { type: 'plain/text' }
);

// Create your file reader
const reader = new FileReader(file);

// Read the whole file
const text = await reader.readAsText('UTF-8');
const dataUrl = await reader.readAsDataURL();
const arrayBuffer = await reader.readAsArrayBuffer();

// Or read binary chunks (ArrayBuffer)
const chunkSize = 8; // bytes
let chunk;
do {
  chunk = await reader.readAsArrayBuffer(chunkSize);
  // do something with the chunk
} while (chunk.byteLength > 0);

About Tanker

This package is a dependency of the Tanker client SDKs for end-to-end encryption:

• @tanker/client-browser for Web applications
• @tanker/client-node for Node.js client applications

Read the documentation to get started.