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A lightweight profanity and bad words checker/sanitizer.


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  • Some fix to the README



Profanity Light

NPM version CircleCI Minified + zipped size

A lightweight and highly customizable profanity cheker. No dictionary is included to reduce the bundle size, and you can add you dictionary fo words with its set of rules!


  • ☁️ Lightweight. No dictionary included to keep the bundle size limited ~1kb!
  • ⚙️ Customizable: each language is different from another so the rule to find bad words. Customize your dictionary to be efficient. Not everyone speaks English 🙂
  • 🔋 Batteries included. Sanitize a word changing each letter or the whole word. Pass your custom replacer. Define any alternative symbol to a letter ( e = e,3,&,é,è...and so on)
  • 💐 Overwrite the single option on each call without the needs to re-instantiate the filter!
  • I mentioned it's written in Typescript?!


yarn add profanity-light


npm i profanity-light


Profanity light comes with an empty dictionary. After you instantiate a filter you can add words to the default dictionary or add one or more dictionaries. Each dictionary comes with its own set of rules. For the moment let's see how to use the default dictionary

import filterFactory from 'profanity-light'; // Instantiate a filter const filter = filterFactory(); // This filter has an empty dictionary included. Let's add some word filter.addWords(['flower']); // Use check to know if a text contains any forbidden word filter.check('A flower is just a flower'); // the above returns true

Adding words: a deep dive

The words you add are checked with a case-insensitive alghoritm, so don't bother to add the upper-case variant. Each word can have many declination like plurals or masculin/feminine. To cover all the cases you can consider that you can add little regural expressions parts in your word

filter.addWords(['flowers?']); // In this case both the singular and plural version of the word are found filter.check('a flower'); // true filter.check('two flowers'); // true

Another example in Italian

filter.addWords(['ca(ne|ni|gn.+)']); filter.check('il cane mi morse'); // true filter.check('i cani abbaiarono'); // true filter.check('le cagne ebbero dei cuccioli'); // true filter.check('il cagnolone era immenso'); // true

You can add a word that contains a space:

filter.addWords(['sun flower']); filter.check('the sun flower is yellow'); // true

or arbitrary spaces

filter.addWords(['sun\\s+flower']); filter.check('the sun flower is yellow'); // true

This very expressive way of defining words will cover most of the cases. Then remember that people are smart... they will find a way 😉

Symbol replacement

Usually a word can be spelled with different characters to overcame a limitation. For example flower can be spelled fl0wer. Each dictionary, included the standard one, has a set of symbol replacements

o = 0 a = 4 @ s = $ e = e é è 3 € & ... and so on

Don't worry to define all the possible characters when defining a word. For example the word flowers? will be matched also against fl0wer and fl0wer$!

Each dictionary can have a different set of symbol replacement, but we'll see this later when we'll add custom dictionaries.

NOTE: If a symbol has a meaning in a regexp, it must be escaped, i.e. '\$' '\{'


Sanitize is a function to replace bad words in a text

filter.sanitize('A flower is a flower'); // this outputs "A ****** is a ******"

You can change the replacement character with the option replacer.

const filter = filterFactory({replacer: 'X'}) filter.sanitize('A flower is a flower'); // this outputs "A XXXXXX is a XXXXXX"

You can decide to replace the entire word with a symbol

const filter = filterFactory({replacer: '***', replaceByWord: true}) filter.sanitize('A flower is a flower'); // this outputs "A *** is a ***"

You can also provide your replace function

const filter = filterFactory({replacer: w => w.split('').reverse().join('')}) filter.sanitize('A flower is a flower'); // this outputs "A rewolf is a rewolf"

The options can also be changed on each call to sanitize

const filter = filterFactory({replacer: 'X'}); // change option on the fly just for this call filter.sanitize('A flower is a flower', undefined, {replacer: '*'}); // this outputs "A ****** is a ******"

Working with more dictionaries

You may want to work with several dictionaries, for example to address different languages. A simple way to do this is to pass a second parameter to each function and specify a dictionary.

filter.addWords(['fiore', 'ape'], 'it');

Since we never created a dictionary called 'it', it is created on the fly here and then reused. The name has no particular meaning, it's just for you. The dictionary is based on the default one. We'll see later how to create a completely different one, for example to define a different set of symbol replacements.

Here an example of check with two different dictionaries.

filter.addWords(['fiore', 'ape'], 'it'); filter.addWords(['fluer', 'abeille'], 'fr'); filter.check('fiore', 'it'); // true, this is a forbidden word in dictionary 'it' filter.check('fiore', 'fr'); // false, this is allowed in dictionary 'fr'

Add a dictionary with its rules

You can create a new dictionary with a set of rules

filter.addDictionary({ name: 'it', words:['fiore', 'ape'], symbolAlternatives: { a: ['4', '@'], // ... } });

A good way to create a dictionary is to directly extend the default one

import { getDefaultDictionary } from 'profanity-light'; const defaultDict = getDefaultDictionary(); filter.addDictionary({ ...defaultDict, name: 'it', words: ['fiore', 'ape'], symbolAlternatives: { ...defaultDict.symbolAlternatives, a: [...defaultDict.symbolAlternatives.a, '4', '@'], // ... } });

Use a filter bound to a dictionary

If you plan to use one specific dictionary you may find annoying to pass everytime the dictionary. You can obtain a filter that is bound to a specific dictionary by using getFilterByDictionary.

import filterFactory from 'profanity-light'; // Instantiate a filter const filter = filterFactory(); // This filter has an empty dictionary included. Let's add some word filter.addWords(['flower'], 'en'); filter.addWords(['fiore'], 'it'); const italianFilter = filter.getFilterByDictionary('it'); // Now every method is bound to the 'it' dictionary and you don't need to specify it anymore italianFilter.check('Un fiore per voi, mia signora'); // true

NOTE: The bounded filters miss the addDictionary and removeDictionary methods.


profanityFactory is a function that creates a filter. It accepts an optionl configuration object with the following properties

  • dictionary?: Dictionary an optional initial dictionary
  • replacer?: Replacer A replacer string or function.
    i.e. '***' or (word) => word.slice(0,2)
    Default: '*'
  • replaceByWord?: boolean If true use the replacer to replace the entire word, otherwise the replace will replace each letter of the word. If the replacer is a function this option is ignored.
    Default: false

A Dictionary is an object with the following properties

  • name: string A mandatory name
  • words: string[] A list of words. Can be empty
  • symbolAlternatives?: { [c: string]: string[] } | null An optional symbol alternatives list

The filter object has the following methods

/** * Check if a text contains profanity. Return true if so. */ check: (text: string, dictionaryName?: string) => boolean; /** * Sanitize a text replacing all profanity with the configured replacer options. * The replacement options can be overwritten through the last parameter, i.e. * sanitize('a text to check', 'en', {replacer: '#!@', replaceByWord: true}) */ sanitize: (text: string, dictionaryName?: string, override?: OverridableProfanityConfig) => string; /** * Add an array of words to a dictionary. * Words can contain regexp like character * i.e. * "flowers?", "bee\w{1}", "d(u|*)cks" */ addWords: (words: string[], dictionaryName?: string) => void; /** * Remove an array of words from a dictionary. */ removeWords: (words: string[], dictionaryName?: string) => void; /** * Return a dictionary. If no name is provided, the default dictionary is returned */ getDictionary: (dictionaryName?: string) => Dictionary; /** * Add a dictionary to the list of dictionaries */ addDictionary: (dictionary: Dictionary) => void; /** * Remove a dictionary from the list of dictionaries */ removeDictionary: (dictionaryName?: string) => void; /** * Clean the content of the dictionary by removing all the saved words and regular expression */ cleanDictionary: (dictionaryName?: string) => void;



Last updated on 25 Oct 2020

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