Introduction to Micromatch

Micromatch is a powerful and flexible library for matching file paths and glob patterns in JavaScript. It enhances the core functionality of glob and minimatch by providing a faster, more accurate, and more intuitive pattern matching algorithm. Whether you’re building a static site generator, a file watcher, or a task runner, Micromatch can help you match files effectively.

Key Features and API Examples

Let’s explore some of the most useful APIs that Micromatch provides along with code snippets for each.

1. Basic Matching

The basic usage of micromatch is similar to other glob libraries:

const micromatch = require('micromatch');
const files = ['a.js', 'a.txt', 'b.js', 'c.md'];
console.log(micromatch(files, '*.js'));
// Output: ['a.js', 'b.js']

2. Brace Expansion

Using brace expansion to match multiple patterns:

console.log(micromatch(['a.js', 'b.txt', 'c.md'], '*.{js,txt}'));
// Output: ['a.js', 'b.txt']

3. Extglobs

Extglobs are extended globs that add additional matching features:

console.log(micromatch(['a.txt', 'b.md', 'c.js'], '*.!(md)'));
// Output: ['a.txt', 'c.js']

4. Negation

Micromatch supports pattern negation as well:

console.log(micromatch(['a.js', 'b.txt', 'c.md'], ['*', '!*.txt']));
// Output: ['a.js', 'c.md']

5. Globstar

Micromatch also handles the double-star (globstar) syntax for matching nested directories:

const files = ['a/b/c.js', 'a/b.txt', 'a/c.md', 'b/a.js'];
console.log(micromatch(files, 'a/**.js'));
// Output: ['a/b/c.js']

6. Match Base

Use the matchBase option to match patterns against the base name of files:

const opts = {matchBase: true};
console.log(micromatch(['a/b/c.js', 'c.md'], '*.js', opts));
// Output: ['a/b/c.js']

Sample Application Using Micromatch

Here’s a simple example of using Micromatch in a file watcher application:

const fs = require('fs');
const micromatch = require('micromatch');

const files = ['index.js', 'style.css', 'README.md', 'app/router.js'];

fs.watch('./', (eventType, filename) => {
  if (filename) {
    if (micromatch([filename], '**/*.{js,css}').length > 0) {
      console.log(`${filename} is a matched file. Event type: ${eventType}`);
    } else {
      console.log(`${filename} does not match any pattern`);
    }
  }
});

This script will watch for changes in the current directory and log a message if the changed file matches the specified patterns (*.js and *.css).

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