@dblechoc/hash-it

hash-it

Fast and consistent hashCode for any object type

Table of contents

• hash-it
  • Table of contents
  • Usage
  • Overview
  • Equality methods
    • hash.is
    • hash.is.all
    • hash.is.any
    • hash.is.not
  • Note
  • Support
    • Browsers
    • Node
  • Development

Usage

// ES2015
import hash from 'hash-it';

// CommonJS
const hash = require('hash-it');

// hash any standard object
console.log(hash({ foo: 'bar' })); // 13729774857125

// or a circular object
console.log(hash(window)); // 3270731309314

Overview

hash-it has a simple goal: provide a fast, consistent, unique hashCode for any object type that is uniquely based on its values. This has a number of uses such as duplication prevention, equality comparisons, blockchain construction, etc.

Any object type?

Yes, any object type. Primitives, ES2015 classes like Symbol, DOM elements (yes, you can even hash the window object if you want). Any object type.

With no exceptions?

Well ... sadly, no, there are a few exceptions.

• Promise
  • There is no way to obtain the values contained within due to its asynchronous nature
• Generator (the result of calling a GeneratorFunction)
  • Like Promise, there is no way to obtain the values contained within due to its dynamic iterable nature
• WeakMap / WeakSet
  • The spec explicitly forbids iteration over them, so the unique values cannot be discovered

In each of these cases, no matter what the values of the object, they will always yield the same hash result, which is unique to each object type. If you have any ideas about how these can be uniquely hashed, they are welcome!

Here is the list of object classes that produce unique hashes:

• Arguments
• Array
• ArrayBuffer
• AsyncFunction (based on toString)
• BigInt
• Boolean
• DataView (based on its buffer)
• Date (based on getTime)
• DocumentFragment (based on outerHTML of all children)
• Error (based on stack)
  • Includes all sub-types (e.g., TypeError, ReferenceError, etc.)
• Event (based on all properties other than Event.timeStamp)
  • Includes all sub-types (e.g., MouseEvent, KeyboardEvent, etc.)
• Float32Array
• Float64Array
• Function (based on toString)
• GeneratorFunction (based on toString)
• Int8Array
• Int16Array
• Int32Array
• HTMLElement (based on outerHTML)
  • Includes all sub-types (e.g., HTMLAnchorElement, HTMLDivElement, etc.)
• Map (order-agnostic)
• Null
• Number
• Object (handles circular objects, order-agnostic)
• Proxy
• RegExp
• Set (order-agnostic)
• String
• SVGElement (based on outerHTML)
  • Includes all sub-types (e.g., SVGRectElement, SVGPolygonElement, etc.)
• Symbol (based on toString)
• Uint8Array
• Uint8ClampedArray
• Uint16Array
• Uint32Array
• Undefined
• Window

If there is an object class or data type that is missing, please submit an issue.

Equality methods

hash.is

hash.is(value1: any, value2: any): boolean

Compares the two objects to determine equality.

console.log(hash.is(null, 123)); // false
console.log(hash.is(null, null)); // true

hash.is.all

hash.is.all(value1: any, value2: any[, value3: any[, ...valueN]]): boolean

Compares the first object to all other objects passed to determine if all are equal based on hashCode

const foo = {
  foo: 'bar',
};
const alsoFoo = {
  foo: 'bar',
};
const stillFoo = {
  foo: 'bar',
};

console.log(hash.is.all(foo, alsoFoo)); // true
console.log(hash.is.all(foo, alsoFoo, stillFoo)); // true

hash.is.any

hash.is.any(value1: any, value2: any[, value3: any[, ...valueN]]): boolean

Compares the first object to all other objects passed to determine if any are equal based on hashCode

const foo = {
  foo: 'bar',
};
const alsoFoo = {
  foo: 'bar',
};
const nopeBar = {
  bar: 'baz',
};

console.log(hash.is.any(foo, alsoFoo)); // true
console.log(hash.is.any(foo, nopeBar)); // false
console.log(hash.is.any(foo, alsoFoo, nopeBar)); // true

hash.is.not

hash.is.not(value1: any, value2: any): boolean

Compares the two objects to determine non-equality.

console.log(hash.is.not(null, 123)); // true
console.log(hash.is.not(null, null)); // false

Note

While the hashes will be consistent when calculated within the same environment, there is no guarantee that the resulting hash will be the same across different environments due to environment-specific or browser-specific implementations of features. This is limited to extreme edge cases, such as hashing the window object, but should be considered if being used with persistence over different environments.

Support

Browsers

• Chrome (all versions)
• Firefox (all versions)
• Edge (all versions)
• Opera 15+
• IE 9+
• Safari 6+
• iOS 8+
• Android 4+

Node

• 4+

Development

Clone the repo and dependencies via yarn. The npm scripts available:

• benchmark => run benchmark of various data types
• benchmark:compare => run benchmark of some data types comparing against other hashing modules
• build => run rollup to build ESM, CJS, and UMD files
• clean => remove files produced from build script
• dev => run webpack dev server to run example app / playground
• lint => run ESLint against all files in the src folder
• lint:fix => run lint script, automatically applying fixable changes
• prepublishOnly => run typecheck, lint, test, and build
• start => alias for dev script
• test => run jest test functions with NODE_ENV=test
• test:coverage => run test with coverage checker
• test:watch => run test with persistent watcher
• typecheck => run tsc to validate internal typings