Trie Prefix Tree

This is a Trie implementation written in JavaScript, with insert and remove capability. It can be used to search a predefined dictionary for prefixes, check a prefix exists and retrieve a list of anagrams and sub-anagrams based on given letters.

What is a Trie?

A Trie (also known as a prefix-tree) is a data structure for storing strings in a tree. Each branch in the tree represents a single character which allows for fast and efficient depth-first searching. Let's say we have a dictionary with the words: CAR, CAT and CURL. We can visualise the trie like this:

Installation

Pull down dependencies:

npm install

This project uses Jest for unit testing and ESLint for linting.

To run combined linting & unit tests:

npm test

To run linting:

npm run lint

Run tests in watch mode:

npm run test-watch

Get code coverage report:

npm run test-coverage

How to Use

To use the Trie, install and save it to your package dependencies:

npm install trie-prefix-tree --save

To create a new Trie:

var trie = require('trie-prefix-tree');

// using ES2015 Modules
import trie from 'trie-prefix-tree';

Instantiate the Trie:

var myTrie = trie(['cat', 'cats', 'dogs', 'elephant', 'tiger']);

Trie functionality:

// retrieve a stringified dump of the Trie object
myTrie.dump(); // { c: { a: { t: $: 1 }, s: 1 ... }}

// optionally pass in spacer parameter to format the output string
myTrie.dump(2); // equivalent of JSON.stringify(obj, null, 2);

// retrieve the Trie object instance
myTrie.tree();

// add a new word to the Trie
myTrie.addWord('lion');

// remove an existing word from the Trie
myTrie.removeWord('dogs');

Adding and removing words can be chained:

myTrie.addWord('hello').removeWord('hello');

Prefix searching:

// check if a prefix exists:
myTrie.isPrefix('do'); // true
myTrie.isPrefix('z'); // false

// count prefixes
myTrie.countPrefix('c'); // 2

// get an array of words with the passed in prefix
myTrie.getPrefix('c'); // ['cat', 'cats']

// Pass false as the second parameter to disable 
// output being sorted alphabetically
// this is useful when your dictionary is already sorted
// and will therefore save performance
myTrie.getPrefix('c', false); // ['cat', 'cats']

// get a random word at a prefix
myTrie.getRandomWordWithPrefix('c'); // 'cat'
myTrie.getRandomWordWithPrefix('c'); // 'cats'

Other:

// retrieve a full list of words in the Trie
// the output array is automatically sorted
myTrie.getWords(); // ['cat', 'cats', 'elephant', 'lion', 'tiger']

// pass false to disable the output being sorted
// this is useful when your dictionary is already sorted
// and will therefore save performance
myTrie.getWords(false); // ['cat', 'cats', 'elephant', 'tiger', 'lion']

// check if a word exists in the Trie
myTrie.hasWord('elephant'); // true
myTrie.hasWord('zoo'); // false

// generate a list of valid anagrams from the given letters
myTrie.getAnagrams('act'); // ['cat'];

// generate a list of valid sub-anagrams from the given letters
myTrie.getSubAnagrams('ctalion'); ['cat', 'cats', 'lion'];

Credits

Credit goes to Kent C. Dodds for providing the awesome 'How to Create an Open Source JavaScript Library' course, available on egghead.io.

License

This project is referenced under the MIT license and is free to use and distribute.

MIT @ Lyndsey Browning