hash-it
Fast and consistent hashCode for any object type
Table of contents
Usage
import hash from "hash-it";
const hash = require("hash-it").default;
const hash = window.hashIt;
console.log(hash({ foo: "bar" }));
console.log(hash(window));
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, I welcome them!
Here is the list of object classes that have been tested and shown to produce unique hashCodes:
Arguments
Array
ArrayBuffer
AsyncFunction
(based on toString
)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
This is basically all I could think of, but if I have missed an object class let me know and I will add it!
Utility functions
is
is(object: any, otherObject: any): boolean
Compares the two objects to determine equality.
console.log(hash.is(null, 123));
console.log(hash.is(null, null));
NOTE: This can also be used with partial-application to create prepared equality comparators.
const isNull = hash.is(null);
console.log(isNull(123));
console.log(isNull(null));
is.all
is.all(object1: any, object2: any[, object3: any[, ...objectN]]): 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));
console.log(hash.is.all(foo, alsoFoo, stillFoo));
NOTE: This can also be used with partial-application to create prepared equality comparators.
const foo = {
foo: "bar"
};
const alsoFoo = {
foo: "bar"
};
const stillFoo = {
foo: "bar"
};
const isAllFoo = hash.is.all(foo);
console.log(isAllFoo(alsoFoo, stillFoo));
is.any
is.any(object1: any, object2: any[, object3: any[, ...objectN]]): 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));
console.log(hash.is.any(foo, nopeBar));
console.log(hash.is.any(foo, alsoFoo, nopeBar));
NOTE: This can also be used with partial-application to create prepared equality comparators.
const foo = {
foo: "bar"
};
const alsoFoo = {
foo: "bar"
};
const nopeBar = {
bar: "baz"
};
const isAnyFoo = hash.is.any(foo);
console.log(isAnyFoo(alsoFoo, nopeBar));
is.not
is.not(object: any, otherObject: any): boolean
Compares the two objects to determine non-equality.
console.log(hash.is.not(null, 123));
console.log(hash.is.not(null, null));
NOTE: This can also be used with partial-application to create prepared equality comparators.
const isNotNull = hash.is.not(null);
console.log(isNotNull(123));
console.log(isNotNull(null));
Gotchas
While the hashes will be consistent when calculated within the same browser environment, there is no guarantee that the hashCode will be the same across different browsers due to browser-specific implementations of features. A vast majority of the time things line up, but there are some edge cases that can cause differences, so just something to be mindful of.
Browser support
- Chrome (all versions)
- Firefox (all versions)
- Edge (all versions)
- Opera 15+
- IE 9+
- Safari 6+
- iOS 8+
- Android 4+
Node support
Development
Standard stuff, clone the repo and npm install
dependencies. The npm scripts available:
build
=> run webpack to build development dist
file with NODE_ENV=developmentbuild:minified
=> run webpack to build production dist
file with NODE_ENV=productiondev
=> run webpack dev server to run example app / playgrounddist
=> runs build
and build:minified
lint
=> run ESLint against all files in the src
folderprepublish
=> runs prepublish:compile
when publishingprepublish:compile
=> run lint
, test:coverage
, transpile:es
, transpile:lib
, dist
test
=> run AVA test functions with NODE_ENV=test
test:coverage
=> run test
but with nyc
for coverage checkertest:watch
=> run test
, but with persistent watchertranspile:lib
=> run babel against all files in src
to create files in lib
transpile:es
=> run babel against all files in src
to create files in es
, preserving ES2015 modules (for
pkg.module
)