@tanker/file-polyfill

A cross-browser polyfill for File

A well known issue with the JavaScript File class is the lack of a constructor in some browsers:

new File(['Hi!'], 'file.txt'); // will throw in Edge and Internet Explorer

Using feature detection, this package will either expose a File polyfill in browsers lacking a proper constructor, or the native File class in others.

You can safely use this package as a drop-in replacement for the native File class in all browsers, e.g.:

import FilePolyfill from '@tanker/file-polyfill';

// Get bits from whatever method you want, using fetch() as an example
const response = await fetch('https://your.server.com/path/to/a/dummy.pdf');
const bits = [await response.arrayBuffer()];

// Construct a file in a cross-browser fashion
const file = new FilePolyfill(bits, 'dummy.pdf', { type: 'application/pdf' });

// Check what we've got
file instanceof window.Blob; // true
file instanceof window.File; // true
file instanceof FilePolyfill; // true
file.name; // 'dummy.pdf'
file.type; // 'application/pdf'
file.size; // the size of dummy.pdf

Note that the polyfill is built with a clever class hierarchy so that instances will appear as regular File and Blob instances, that can be used with FileReader and other APIs working with files.

Sponsored by Tanker.