identifier-regex

library1.0.1jsnpmunverified

The `identifier-regex` package provides a precise regular expression function, `identifierRegex()`, designed to match valid JavaScript identifiers according to the ECMAScript specification. This includes proper handling of reserved words and specific syntax rules. The current stable version is 1.0.1, focusing on correctness and stability rather than rapid feature additions. Its primary differentiator is its strict adherence to JavaScript identifier rules, offering an `exact` option to control whether the regex matches the entire string or finds identifiers within a larger text. It explicitly excludes global properties like `Infinity` from being considered valid identifiers, aligning with common usage expectations. This library is ideal for parsers, linters, or any application needing to validate or extract JavaScript identifiers reliably.

testing

npm install identifier-regex

github ↗package ↗

INSTALL

IMPORT

SIG · IDENTIFIER-REGEX

identifier-regex

testingjavascriptv1.0.1

Install

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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.

identifierRegex

✓ import identifierRegex from 'identifier-regex';

✗ const identifierRegex = require('identifier-regex');

This package is primarily designed for ES modules. While CommonJS might work with transpilation, direct `require` is not the recommended or native approach since Node.js >=18 engine requirement.

RegExp instance

✓ const myIdentifierRegex = identifierRegex();

✗ identifierRegex.test('foo');

The `identifierRegex` function *returns* a new `RegExp` instance each time it's called. You must call it to get the regex object to use `test()`, `match()`, etc.

identifierRegex with options

✓ import identifierRegex from 'identifier-regex'; const looseRegex = identifierRegex({ exact: false });

✗ import { identifierRegex } from 'identifier-regex';

The package exports a default function. Attempting a named import for `identifierRegex` will result in an error. Options are passed as an object to the function call.

Demonstrates importing the `identifierRegex` function, using it to test strings for identifier validity (including reserved words), and extracting identifiers from longer strings with the `exact: false` option, while also showing it returns a `RegExp` instance.

import identifierRegex from 'identifier-regex'; // Basic usage: testing if a string is a valid identifier console.log("Is 'foo' a valid identifier?", identifierRegex().test('foo')); //=> true console.log("Is '1kg' a valid identifier?", identifierRegex().test('1kg')); //=> false (Identifiers cannot start with a number) console.log("Is 'await' a valid identifier?", identifierRegex().test('await')); //=> false (Reserved word) // Using 'exact: false' to find identifiers within a larger string const textWithIdentifiers = 'function _myVar_($param1) { const $var2 = 1; }'; const identifiersInText = textWithIdentifiers.match(identifierRegex({ exact: false, global: true })); console.log(`Identifiers found in "${textWithIdentifiers}":`, identifiersInText); //=> ['_myVar_', '$param1', '$var2'] // Demonstrate that calling identifierRegex() returns a RegExp instance const myRegexInstance = identifierRegex(); console.log('Type of returned value:', typeof myRegexInstance); console.log('Is it a RegExp instance?', myRegexInstance instanceof RegExp);

Debug

Known issues

gotchaWhen running the regex against untrusted user input in a server context, it is strongly recommended to give the regex a timeout (e.g., using `super-regex`) to prevent potential Regular Expression Denial of Service (ReDoS) attacks. While the package maintainer does not consider ReDoS a direct vulnerability for this specific package, it's a critical security consideration for user-facing applications.

fix

Integrate with a regex timeout library like `super-regex` when processing untrusted input.

affects: >=1.0.0

gotchaThe regex will NOT match properties of the global object like `globalThis`, `Infinity`, `NaN`, and `undefined` as valid identifiers. While these are JavaScript built-ins, the library's design choice is to exclude them from identifier matching, which might surprise users expecting a broader match.

fix

If you need to match these global properties specifically, you will need to augment the result of `identifierRegex()` with additional patterns or handle them separately.

affects: >=1.0.0

gotchaThe default `exact` option for `identifierRegex()` is `true`. This means the regex will only match if the entire input string is a valid JavaScript identifier. If you intend to find or extract identifiers from within a larger string (e.g., `'foo bar'.match(identifierRegex())`), you must explicitly set `{ exact: false }`.

fix

Pass `{ exact: false }` to the `identifierRegex` function when matching substrings: `identifierRegex({ exact: false }).test('foo bar')`.

affects: >=1.0.0

Errors

Common errors & fixes

TypeError: identifierRegex is not a function

Attempting to use the `identifierRegex` function directly as a `RegExp` object without calling it first (e.g., `identifierRegex.test('foo')`). The function returns a RegExp instance.

fix

Call `identifierRegex()` to obtain the regular expression object: `identifierRegex().test('foo')`.

SyntaxError: Cannot use import statement outside a module

Attempting to use ES module `import` syntax in a CommonJS (CJS) environment without proper configuration (e.g., without `'type': 'module'` in `package.json` for Node.js).

fix

Ensure your project is configured as an ES module by adding `'type': 'module'` to your `package.json`, or use a bundler that transpiles ES modules to CJS for older environments. This package requires Node.js >=18, which has robust ESM support.

My regex isn't matching anything in a longer string (e.g., 'foo bar').

The default `exact` option is `true`, meaning the regex tries to match the entire input string. `'foo bar'` is not a single, exact identifier.

fix

Set the `exact` option to `false` when you want to find identifiers within a larger string: `identifierRegex({ exact: false }).test('foo bar')`.

Upgrade

Version history

1.0.1latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

9 hits · last 30 days

node

Amazon

Resources

githubhttps://github.com/sindresorhus/identifier-regex ↗

packagehttps://www.npmjs.com/package/identifier-regex ↗