jest-haste-map

jest-haste-map

jest-haste-map is a module used by Jest, a popular JavaScript testing framework, to create a fast lookup of files in a project. It helps Jest efficiently locate and track changes in files during testing, making it particularly useful for large projects with many files.

why jest-haste-map ?

• Parallel crawling and analysis: jest-haste-map crawls the entire project, extracts dependencies, and analyzes files in parallel across worker processes.This can significantly improve the performance of the map building process.
• Cached file system: jest-haste-map keeps a cache of the file system in memory and on disk. This allows for fast file related operations, such as resolving module imports and checking for changes.
• Minimal work: jest-haste-map only does the minimal amount of work necessary when files change. When using watchman (recommended for large projects), Jest asks watchman for changed files instead of crawling the file system. Without watchman, @parcel/watcher is used — it picks the best native backend for the platform (fs-events on macOS, inotify on Linux, windows on Windows).
• File system watching: jest-haste-map can watch the file system for changes. This is useful for building interactive tools, such as watch mode.

Installation

with npm :

npm install jest-haste-map --save-dev

with yarn :

yarn add jest-haste-map --dev

usage

jest-haste-map is compatible with both ES modules and CommonJS

simple usage

const map = new HasteMap.default({
  // options
});

Example usage (get all files with .js extension in the project)

import HasteMap from 'jest-haste-map';
import os from 'os';
import {dirname} from 'path';
import {fileURLToPath} from 'url';

const root = dirname(fileURLToPath(import.meta.url));

const map = new HasteMap.default({
  id: 'myproject', //Used for caching.
  extensions: ['js'], // Tells jest-haste-map to only crawl .js files.
  maxWorkers: os.availableParallelism(), //Parallelizes across all available CPUs.
  platforms: [], // This is only used for React Native, you can leave it empty.
  roots: [root], // Can be used to only search a subset of files within `rootDir`
  retainAllFiles: true,
  rootDir: root, //The project root.
});

const {hasteFS} = await map.build();

const files = hasteFS.getAllFiles();

console.log(files);

options

For more, you can check github