@file-services/overlay
Overlay files and directories from one file system on top of another.
Motivation
Overlay file system allows taking a native node file system ("lower fs") and overlay files and directories from an in-memory file system ("higher fs"). It can be used as a virtual layer providing a solution for storing and manipulating temporary data.
Behavior
Read operations (readFile
, readdir
, stat
, etc.) are checking higher fs first, and fallback to lower fs.
Currently, all write operations go directly to the original lower fs.
Getting started
Install library in project:
yarn add @file-services/overlay
Then, use the programmatic API:
import { createOverlayFs } from '@file-services/overlay';
import { createMemoryFs } from '@file-services/memory';
import { nodeFs } from '@file-services/node';
const memFs = createMemoryFs({
src: {
'a.txt': `A`,
'b.txt': `B`,
},
});
const overlayFs = createOverlayFs(nodeFs , memFs );
createOverlayFs
also accepts a directory path as third parameter which specifies which directory in lower fs should be overlaid upon (defaults to lowerFs.cwd()
). This is important when overlaying a memory fs over native node fs and running on Windows. Memory fs uses posix-style paths, so the base directory is where memory's root /
begins to overlay.
License
MIT