Negative Regular Expression Generator

Common errors

• ReferenceError: require is not defined

  cause Attempting to use `require()` in an ES Modules (ESM) context without a transpiler or specific Node.js configuration.
  fix If your project is ESM-first, try `import not from 'regex-not';` (though this package is CJS-primary, Node.js often handles this for default exports). Alternatively, convert your file to CommonJS if possible, or configure a bundler (like Webpack or Rollup) to handle CJS modules in an ESM project.

• My regex doesn't work as expected; it matches strings that contain the pattern I want to exclude!

  cause Misunderstanding the default 'strict' matching behavior of `regex-not`. By default, it excludes only exact matches, not partial containment.
  fix If you want the regex to match strings that *do not contain* a specific substring, you need to use the `contains` option: `not('your_pattern', { contains: true })`.

Warnings

• gotcha The package is primarily designed for CommonJS (CJS) environments and uses `require()`. Direct `import` statements in ES Modules (ESM) will likely fail without a bundler or specific Node.js configuration for CJS interoperability.
  Fix: Use `const not = require('regex-not');` in CJS files. For ESM, you might need to use `import not from 'regex-not';` but be aware that it relies on Node.js's CJS-ESM interoperability or a bundler's transpilation.
• gotcha By default, `regex-not` generates a regex for *strict* negation, meaning it matches if the input string does NOT *exactly equal* the pattern. If you intend to match strings that do NOT *contain* a substring, you must explicitly set `options.contains: true`.
  Fix: For substring negation, call `not(string, { contains: true })`. For example, `not('foo', { contains: true })` will return a regex that doesn't match 'foobar'.
• gotcha The package's low version (1.0.2) and infrequent updates indicate it's in maintenance mode. While stable for its current functionality, it may not receive updates for new JavaScript features, performance optimizations, or modern API patterns.
  Fix: Evaluate if the current functionality meets your needs without expecting future feature enhancements or major refactorings to adopt newer JS standards like native ESM.

Install

• npm install regex-not npm
• yarn add regex-not yarn
• pnpm add regex-not pnpm

Imports

• not
  wrong:

  import not from 'regex-not';

  correct:

  const not = require('regex-not');

  The package is primarily CommonJS. For ESM, bundlers or a wrapper might be necessary. The default export is the `not` function.
• not.create
  wrong:

  import { create } from 'regex-not';

  correct:

  const not = require('regex-not');
  const regexString = not.create('foo');

  `.create` is a property on the default `not` function, not a separate named export. It returns the regex pattern string.

Quickstart

Demonstrates strict (default) and 'contains' negation using the `not` function, and how to get the raw regex pattern string using `not.create`.

const not = require('regex-not');

// Default behavior: matches if the string does NOT exactly equal 'foo'
const reStrict = not('foo');
console.log('Strict matching:');
console.log(`'foo' should be false: ${reStrict.test('foo')}`);     // Expected: false
console.log(`'bar' should be true: ${reStrict.test('bar')}`);     // Expected: true
console.log(`'foobar' should be true: ${reStrict.test('foobar')}`); // Expected: true (not exact)

// Option: matches if the string does NOT contain 'foo'
const reContains = not('foo', { contains: true });
console.log('\nContains matching:');
console.log(`'foo' should be false: ${reContains.test('foo')}`);     // Expected: false
console.log(`'bar' should be true: ${reContains.test('bar')}`);     // Expected: true
console.log(`'foobar' should be false: ${reContains.test('foobar')}`); // Expected: false (contains 'foo')

// Get just the regex pattern string
const patternString = not.create('bar');
console.log(`\nGenerated pattern string for 'bar': ${patternString}`);
const customRegExp = new RegExp(patternString);
console.log(`Using custom RegExp: '${customRegExp.source}'.test('bar') should be false: ${customRegExp.test('bar')}`);