├── .npmrc ├── .gitattributes ├── .gitignore ├── .editorconfig ├── index.d.ts ├── index.js ├── .github └── workflows │ └── main.yml ├── test.js ├── license ├── package.json └── readme.md /.npmrc: -------------------------------------------------------------------------------- 1 | package-lock=false 2 | -------------------------------------------------------------------------------- /.gitattributes: -------------------------------------------------------------------------------- 1 | * text=auto eol=lf 2 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | node_modules 2 | yarn.lock 3 | -------------------------------------------------------------------------------- /.editorconfig: -------------------------------------------------------------------------------- 1 | root = true 2 | 3 | [*] 4 | indent_style = tab 5 | end_of_line = lf 6 | charset = utf-8 7 | trim_trailing_whitespace = true 8 | insert_final_newline = true 9 | 10 | [*.yml] 11 | indent_style = space 12 | indent_size = 2 13 | -------------------------------------------------------------------------------- /index.d.ts: -------------------------------------------------------------------------------- 1 | /** 2 | Check if a string is a valid [JavaScript identifier](https://developer.mozilla.org/en-US/docs/Glossary/Identifier). 3 | 4 | @example 5 | ``` 6 | import isIdentifier from 'is-identifier'; 7 | 8 | isIdentifier('foo'); 9 | //=> true 10 | 11 | isIdentifier('1kg'); 12 | //=> false 13 | 14 | isIdentifier('await'); // Reserved identifier 15 | //=> false 16 | ``` 17 | */ 18 | export default function isIdentifier(value: string); 19 | -------------------------------------------------------------------------------- /index.js: -------------------------------------------------------------------------------- 1 | import identifierRegex from 'identifier-regex'; 2 | import {isMatch} from 'super-regex'; 3 | 4 | const regex = identifierRegex(); 5 | 6 | export default function isIdentifier(value) { 7 | if (typeof value !== 'string') { 8 | throw new TypeError(`Expected a string, got \`${typeof value}\`.`); 9 | } 10 | 11 | // Prevent abuse. 12 | if (value.length > 100_000) { 13 | return false; 14 | } 15 | 16 | return isMatch(regex, value, {timeout: 1000}); 17 | } 18 | -------------------------------------------------------------------------------- /.github/workflows/main.yml: -------------------------------------------------------------------------------- 1 | name: CI 2 | on: 3 | - push 4 | - pull_request 5 | jobs: 6 | test: 7 | name: Node.js ${{ matrix.node-version }} 8 | runs-on: ubuntu-latest 9 | strategy: 10 | fail-fast: false 11 | matrix: 12 | node-version: 13 | - 22 14 | - 18 15 | steps: 16 | - uses: actions/checkout@v4 17 | - uses: actions/setup-node@v4 18 | with: 19 | node-version: ${{ matrix.node-version }} 20 | - run: npm install 21 | - run: npm test 22 | -------------------------------------------------------------------------------- /test.js: -------------------------------------------------------------------------------- 1 | import test from 'ava'; 2 | import isIdentifier from './index.js'; 3 | 4 | const validItems = [ 5 | 'unicorn', 6 | '$foo', 7 | 'foo_bar', 8 | ]; 9 | 10 | const invalidItems = [ 11 | 'true', 12 | 'undefined', 13 | '1foo', 14 | ' foo', 15 | 'foo-bar', 16 | ]; 17 | 18 | test('valid', t => { 19 | for (const valid of validItems) { 20 | t.true(isIdentifier(valid), valid); // eslint-disable-line ava/assertion-arguments 21 | } 22 | }); 23 | 24 | test('invalid', t => { 25 | for (const invalid of invalidItems) { 26 | t.false(isIdentifier(invalid), invalid); // eslint-disable-line ava/assertion-arguments 27 | } 28 | }); 29 | -------------------------------------------------------------------------------- /license: -------------------------------------------------------------------------------- 1 | MIT License 2 | 3 | Copyright (c) Sindre Sorhus (https://sindresorhus.com) 4 | 5 | Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: 6 | 7 | The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. 8 | 9 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 10 | -------------------------------------------------------------------------------- /package.json: -------------------------------------------------------------------------------- 1 | { 2 | "name": "is-identifier", 3 | "version": "1.0.1", 4 | "description": "Check if a string is a valid JavaScript identifier", 5 | "license": "MIT", 6 | "repository": "sindresorhus/is-identifier", 7 | "funding": "https://github.com/sponsors/sindresorhus", 8 | "author": { 9 | "name": "Sindre Sorhus", 10 | "email": "sindresorhus@gmail.com", 11 | "url": "https://sindresorhus.com" 12 | }, 13 | "type": "module", 14 | "exports": { 15 | "types": "./index.d.ts", 16 | "default": "./index.js" 17 | }, 18 | "sideEffects": false, 19 | "engines": { 20 | "node": ">=18" 21 | }, 22 | "scripts": { 23 | "test": "xo && ava" 24 | }, 25 | "files": [ 26 | "index.js", 27 | "index.d.ts" 28 | ], 29 | "keywords": [ 30 | "identifier", 31 | "keyword", 32 | "word", 33 | "check", 34 | "test", 35 | "reserved", 36 | "javascript", 37 | "ecmascript", 38 | "variable", 39 | "function", 40 | "property", 41 | "is", 42 | "valid" 43 | ], 44 | "dependencies": { 45 | "identifier-regex": "^1.0.0", 46 | "super-regex": "^1.0.0" 47 | }, 48 | "devDependencies": { 49 | "ava": "^6.1.2", 50 | "xo": "^0.58.0" 51 | } 52 | } 53 | -------------------------------------------------------------------------------- /readme.md: -------------------------------------------------------------------------------- 1 | # is-identifier 2 | 3 | > Check if a string is a valid [JavaScript identifier](https://developer.mozilla.org/en-US/docs/Glossary/Identifier) 4 | 5 | ## Install 6 | 7 | ```sh 8 | npm install is-identifier 9 | ``` 10 | 11 | ## Usage 12 | 13 | ```js 14 | import isIdentifier from 'is-identifier'; 15 | 16 | isIdentifier('foo'); 17 | //=> true 18 | 19 | isIdentifier('1kg'); 20 | //=> false 21 | 22 | isIdentifier('await'); // Reserved identifier 23 | //=> false 24 | ``` 25 | 26 | > [!NOTE] 27 | > Although `globalThis`, `Infinity`, `NaN`, and `undefined` are [properties of the global object](https://tc39.es/ecma262/#sec-value-properties-of-the-global-object) and not identifiers, they are treated as reserved here because they should generally not be used as identifiers. 28 | 29 | ## API 30 | 31 | ### isIdentifier(value) 32 | 33 | Returns a boolean for whether the given value is a valid JavaScript identifier. 34 | 35 | ## Related 36 | 37 | - [to-valid-identifier](https://github.com/sindresorhus/to-valid-identifier) - Convert a string to a valid JavaScript identifier 38 | - [identifier-regex](https://github.com/sindresorhus/identifier-regex) - Regular expression for matching valid JavaScript identifiers 39 | - [reserved-identifiers](https://github.com/sindresorhus/reserved-identifiers) - Provides a list of reserved identifiers for JavaScript 40 | --------------------------------------------------------------------------------