Registry / testing / browserslist-useragent-regexp

browserslist-useragent-regexp

library4.1.4jsnpmunverified

browserslist-useragent-regexp is a utility that compiles a `browserslist` query into a JavaScript regular expression, enabling client-side user agent detection. This allows developers to determine if a browser supports a given `browserslist` configuration directly in the browser, without server-side checks. It is currently at version 4.1.4 and receives active maintenance, with frequent bug fixes and minor feature releases. Key differentiators include its direct integration with `browserslist` for consistent browser targeting across toolchains and its ability to generate optimized regex patterns. Since version 4.0.0, it is an ESM-only package and requires Node.js >= 14. This library is particularly useful for conditional loading of polyfills or different JavaScript bundles based on client-side browser capabilities.

testing

npm install browserslist-useragent-regexp

github ↗package ↗

INSTALL

IMPORT

SIG · BROWSERSLIST-USERA

browserslist-useragent-regexp

testingjavascriptv4.1.4

Install

—

Import

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Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

browserslistUseragentRegexp

✓ import { browserslistUseragentRegexp } from 'browserslist-useragent-regexp';

✗ const browserslistUseragentRegexp = require('browserslist-useragent-regexp');

The package is ESM-only since v4.0.0. The primary function to programmatically generate the regex is `browserslistUseragentRegexp`.

RegExp from generated file

✓ import supportedBrowsersRegex from './supportedBrowsers.js';

A common usage pattern is to use the `browserslist-useragent-regexp` CLI to generate a JavaScript file (e.g., `supportedBrowsers.js`) that exports the compiled RegExp as a default export.

Type for function options

✓ import type { Options } from 'browserslist-useragent-regexp';

TypeScript types are shipped with the package for its programmatic API, allowing for type-safe usage of the options object.

This quickstart demonstrates the common pattern of using the CLI to generate a JavaScript file containing the compiled RegExp, which is then imported and used to test a user agent string. It includes setup for the `.browserslistrc` and a `package.json` script, along with example runtime usage.

/* .browserslistrc */ // last 2 versions // not dead /* package.json */ // { // "scripts": { // "generate-regex": "echo \"export default $(browserslist-useragent-regexp --allowHigherVersions);\" > supportedBrowsers.js" // } // } // Run in your terminal once: // npm run generate-regex // --- supportedBrowsers.js (generated) --- // export default /Edge?\/(10[5-9]|1[1-9]\d|[2-9]\d\d|...)/; /* (actual regex will vary) */ // --- your-app.js --- import supportedBrowsersRegex from './supportedBrowsers.js'; function checkBrowserSupport() { const userAgent = typeof navigator !== 'undefined' ? navigator.userAgent : process.env.USER_AGENT ?? ''; if (userAgent === '') { console.warn('User-Agent string is empty. Cannot perform check.'); return; } if (supportedBrowsersRegex.test(userAgent)) { console.log(`User agent '${userAgent}' is supported.`); } else { console.warn(`User agent '${userAgent}' is NOT supported.`); } } // Example usage (replace with actual user agent for testing) process.env.USER_AGENT = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36'; checkBrowserSupport(); process.env.USER_AGENT = 'Mozilla/5.0 (Windows NT 6.1; Trident/7.0; rv:11.0) like Gecko'; // IE 11 (likely unsupported) checkBrowserSupport();

Debug

Known issues

breakingThe package moved to ESM-only and dropped CommonJS support. Attempting to `require()` the package will result in an `ERR_REQUIRE_ESM` error.

fix

Migrate your import statements to use ES module syntax (e.g., `import ... from 'package';`). Ensure your project is configured for ESM, potentially by adding `"type": "module"` to `package.json` or using `.mjs` file extensions.

affects: >=4.0.0

breaking`browserslist` is no longer a direct dependency but a peer dependency. It must be installed separately in your project.

fix

Ensure `browserslist` is installed as a dependency in your project: `npm install browserslist` or `pnpm add browserslist`.

affects: >=4.0.0

breakingThe minimum required Node.js version was bumped to 14. Projects running on older Node.js versions will encounter compatibility issues.

fix

Upgrade your Node.js environment to version 14 or higher.

affects: >=4.0.0

breakingNaming conventions within the JavaScript API changed from `regexp` to `regex`. If you were programmatically using properties or options with `regexp` in their name, they are now `regex`.

fix

Review your programmatic usage of the library and update any references from `regexp` to `regex` in option keys or properties.

affects: >=4.0.0

breakingThe minimum required Node.js version was bumped to 12.

fix

Upgrade your Node.js environment to version 12 or higher.

affects: >=3.0.0 <4.0.0

gotchaWhen using the programmatic API (`browserslistUseragentRegexp`), you must either specify `browsers` in the options object or have a `.browserslistrc` file present in your project, otherwise, the `browserslist` query resolution will fail.

fix

Pass a `browsers` array to the `browserslistUseragentRegexp` function options or ensure a valid `.browserslistrc` file is in your project's root or configured location.

affects: >=2.0.0

Errors

Common errors & fixes

Error [ERR_REQUIRE_ESM]: require() of ES module 'browserslist-useragent-regexp' from ... not supported.

Attempting to import an ESM-only package using CommonJS `require()` syntax.

fix

Change `const someVar = require('browserslist-useragent-regexp');` to `import { someVar } from 'browserslist-useragent-regexp';`. Ensure your project's `package.json` has `"type": "module"` or use `.mjs` file extensions for ESM files.

TypeError: The 'browsers' option is required.

The `browserslistUseragentRegexp` function was called without providing a `browsers` array in its options or without a resolvable `.browserslistrc` configuration.

fix

Provide a `browsers` array in the options object (e.g., `browserslistUseragentRegexp({ browsers: ['last 2 versions'] })`) or ensure a `.browserslistrc` file is correctly configured in your project.

Error: Cannot find package 'browserslist'. Did you mean to install it?

The `browserslist` package, a peer dependency since v4.0.0, is not installed in the project.

fix

Install `browserslist` in your project: `npm install browserslist` or `pnpm add browserslist`.

Upgrade

Version history

4.1.4latest on npm

Audit

Dependencies

browserslistrequiredRequired as a peer dependency since v4.0.0 to resolve browser queries.

Agent activity

17 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/browserslist/browserslist-useragent-regexp ↗

packagehttps://www.npmjs.com/package/browserslist-useragent-regexp ↗