hashids

What is hashids?

The hashids npm package is a small JavaScript library that generates short, unique, non-sequential ids from numbers. It is useful for creating URL-friendly ids, obfuscating database ids, and more.

What are hashids's main functionalities?

Encoding Numbers

This feature allows you to encode a single number into a unique, short string. This is useful for creating URL-friendly ids.

const Hashids = require('hashids/cjs');
const hashids = new Hashids();
const id = hashids.encode(12345);
console.log(id); // e.g., 'NkK9'

Decoding Numbers

This feature allows you to decode a previously encoded string back into the original number. This is useful for retrieving the original id from a URL-friendly id.

const Hashids = require('hashids/cjs');
const hashids = new Hashids();
const numbers = hashids.decode('NkK9');
console.log(numbers); // [12345]

Encoding Multiple Numbers

This feature allows you to encode multiple numbers into a single unique string. This can be useful for combining multiple ids into one.

const Hashids = require('hashids/cjs');
const hashids = new Hashids();
const id = hashids.encode(1, 2, 3);
console.log(id); // e.g., 'laHquq'

Decoding Multiple Numbers

This feature allows you to decode a previously encoded string back into the original set of numbers. This is useful for retrieving multiple ids from a single URL-friendly id.

const Hashids = require('hashids/cjs');
const hashids = new Hashids();
const numbers = hashids.decode('laHquq');
console.log(numbers); // [1, 2, 3]

Custom Alphabet

This feature allows you to specify a custom alphabet for encoding. This can be useful for ensuring that the generated ids meet specific requirements or constraints.

const Hashids = require('hashids/cjs');
const hashids = new Hashids('', 0, 'abcdefghijklmnopqrstuvwxyz');
const id = hashids.encode(12345);
console.log(id); // e.g., 'dplb'

Other packages similar to hashids

shortid

The shortid package generates short, unique, non-sequential ids. It is similar to hashids in that it creates URL-friendly ids, but it does not provide the ability to encode and decode numbers.

nanoid

The nanoid package is a tiny, secure, URL-friendly, unique string ID generator. It is similar to hashids in that it creates short, unique ids, but it focuses on security and performance rather than encoding and decoding numbers.

uuid

The uuid package generates RFC-compliant UUIDs (Universally Unique Identifiers). It is different from hashids in that it generates longer, globally unique ids, and does not provide the ability to encode and decode numbers.

README

Hashids is small JavaScript library to generate YouTube-like ids from numbers. Use it when you don't want to expose your database ids to the user: http://hashids.org/javascript

Getting started

Install Hashids via:

yarn add hashids

(or just directly use the code at dist/hashids.js)

Use in ESM-compatible environments (webpack, modern browsers)

import Hashids from 'hashids'
const hashids = new Hashids()

console.log(hashids.encode(1))

Use in CommonJS environments (most often Node.js)

const Hashids = require('hashids/cjs')
const hashids = new Hashids()

console.log(hashids.encode(1))

Note: When using Node that supports conditional exports, require('hashids') (version >=13) will also work.

Use as global in the browser (wherever ES6 is supported; 5KB)

<script type="text/javascript" src="hashids.min.js"></script>
<script type="text/javascript">

    var hashids = new Hashids();
    console.log(hashids.encode(1));

</script>

Use in TypeScript:

import or require, based on the environment (see above). If you want to use the CommonJS module syntax (require), you'll need to install the Node.js types from the DefinitelyTyped repository.

npm install @types/node

If you want to use the ESM syntax (import Hashids from 'hashids'), you will need to include the following options in your tsconfig.json.

{
  "allowSyntheticDefaultImports": true,
  "esModuleInterop": true
}

The above is not required if you import the CommonJS version directly: import Hashids from 'hashids/cjs'.

If you get errors stating: Cannot find name 'BigInt', add "esnext.bigint" or "esnext" to your tsconfig.json file, under "lib":

{
  "compilerOptions": {
    ...
    "lib": [
      "esnext.bigint",
      ...
    ]
  }
}

Note that your environment doesn't actually have to support BigInt for hashids to function.

Quick example

const hashids = new Hashids()

const id = hashids.encode(1, 2, 3) // o2fXhV
const numbers = hashids.decode(id) // [1, 2, 3]

More options

A few more ways to pass to encode():

const hashids = new Hashids()

console.log(hashids.encode(1, 2, 3)) // o2fXhV
console.log(hashids.encode([1, 2, 3])) // o2fXhV
// strings containing integers are coerced to numbers:
console.log(hashids.encode('1', '2', '3')) // o2fXhV
console.log(hashids.encode(['1', '2', '3'])) // o2fXhV
// BigInt support:
console.log(hashids.encode([1n, 2n, 3n])) // o2fXhV
// Hex notation BigInt:
console.log(hashids.encode([0x1n, 0x2n, 0x3n])) // o2fXhV

Make your ids unique:

Pass a "salt" to make your ids unique (e.g. a project name):

var hashids = new Hashids('My Project')
console.log(hashids.encode(1, 2, 3)) // Z4UrtW

var hashids = new Hashids('My Other Project')
console.log(hashids.encode(1, 2, 3)) // gPUasb

Use padding to make your ids longer:

Note that ids are only padded to fit at least a certain length. It doesn't mean that your ids will be exactly that length.

const hashids = new Hashids() // no padding
console.log(hashids.encode(1)) // jR

const hashids = new Hashids('', 10) // pad to length 10
console.log(hashids.encode(1)) // VolejRejNm

Pass a custom alphabet:

const hashids = new Hashids('', 0, 'abcdefghijklmnopqrstuvwxyz') // all lowercase
console.log(hashids.encode(1, 2, 3)) // mdfphx

Default alphabet is abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890.

Since v2.0 you can even use emojis as the alphabet.

Encode hex instead of numbers:

Useful if you want to encode numbers like Mongo's ObjectIds.

Note that there is no limit on how large of a hex number you can pass.

var hashids = new Hashids()

var id = hashids.encodeHex('507f1f77bcf86cd799439011') // y42LW46J9luq3Xq9XMly
var hex = hashids.decodeHex(id) // 507f1f77bcf86cd799439011

Please note that this is not the equivalent of:

const hashids = new Hashids()

const id = Hashids.encode(BigInt('0x507f1f77bcf86cd799439011')) // y8qpJL3ZgzJ8lWk4GEV
const hex = Hashids.decode(id)[0].toString(16) // 507f1f77bcf86cd799439011

The difference between the two is that the built-in encodeHex will always result in the same length, even if it contained leading zeros.

For example hashids.encodeHex('00000000') would encode to qExOgK7 and decode back to '00000000' (length information is preserved).

Pitfalls

1. When decoding, output is always an array of numbers (even if you encode only one number):

   const hashids = new Hashids()
   
   const id = hashids.encode(1)
   console.log(hashids.decode(id)) // [1]
   

2. Encoding negative numbers is not supported.

3. If you pass bogus input to encode(), an empty string will be returned:

   const hashids = new Hashids()
   
   const id = hashids.encode('123a')
   console.log(id === '') // true
   

4. Do not use this library as a security tool and do not encode sensitive data. This is not an encryption library.

Randomness

The primary purpose of Hashids is to obfuscate ids. It's not meant or tested to be used as a security or compression tool. Having said that, this algorithm does try to make these ids random and unpredictable:

No repeating patterns showing there are 3 identical numbers in the id:

const hashids = new Hashids()
console.log(hashids.encode(5, 5, 5)) // A6t1tQ

Same with incremented numbers:

const hashids = new Hashids()

console.log(hashids.encode(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)) // wpfLh9iwsqt0uyCEFjHM

console.log(hashids.encode(1)) // jR
console.log(hashids.encode(2)) // k5
console.log(hashids.encode(3)) // l5
console.log(hashids.encode(4)) // mO
console.log(hashids.encode(5)) // nR

Curses! #$%@

This code was written with the intent of placing created ids in visible places, like the URL. Therefore, by default the algorithm tries to avoid generating most common English curse words by generating ids that never have the following letters next to each other:

c, f, h, i, s, t, u

You may customize the chars that shouldn't be placed next to each other by providing a 4th argument to the Hashids constructor:

// first 4 arguments will fallback to defaults (empty salt, no minimum length, default alphabet)
const hashids = new Hashids(undefined, undefined, undefined, 'zyxZYX')

BigInt

If your environment supports BigInt, you can use the standard API to encode and decode them the same way as ordinary numbers.

Trying to decode a BigInt-encoded hashid on an unsupported environment will throw an error.

License

MIT License. See the LICENSE file. You can use Hashids in open source projects and commercial products. Don't break the Internet. Kthxbye.