hash-it

Fast and consistent hashCode for any object type

Table of contents

• hash-it
  • Table of contents
  • Usage
  • Overview
  • Hash consistency
  • Support
    • Browsers
    • Node
  • Development

Usage

1// ES2015
2import hash from 'hash-it';
3
4// CommonJS
5const hash = require('hash-it');
6
7// hash any standard object
8console.log(hash({ foo: 'bar' })); // 13729774857125
9
10// or a circular object
11console.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. Here is the list of object classes that produce consistent, unique hashes based on their value:

• Arguments
• Array
• ArrayBuffer
• AsyncFunction (based on toString)
• AsyncGeneratorFunction (based on toString)
• BigInt
• BigInt64Array
• BigUint64Array
• 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)
• SharedArrayBuffer
• String
• SVGElement (based on outerHTML)
  • Includes all sub-types (e.g., SVGRectElement, SVGPolygonElement, etc.)
• Symbol (based on toString)
• Uint8Array
• Uint8ClampedArray
• Uint16Array
• Uint32Array
• Undefined
• Window

Are there any exceptions?

Sadly, yes, there are a few scenarios where internal values cannot be introspected for the object. In this case, the object is hashed based on its class type and reference.

• 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 / WeakRef / WeakSet
  • The spec explicitly forbids iteration over them, so the unique values cannot be discovered

1const promise = Promise.resolve(123);
2
3console.log(hash(promise)); // 16843037491939
4console.log(hash(promise)); // 16843037491939
5console.log(hash(Promise.resolve(123))); // 4622327363876

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

Hash consistency

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