obj-eql

Compare two objects for equality, with support for custom comparison functions.

Installation

$ npm install obj-eql --save

Usage

var objEql = require('obj-eql')
var x = {a:1}
var y = {a:1}
x === y // => false
objEql(x, y) // => true

objEql([compisonFunction, ]objectA, objectB)

Arguments

• comparisonFunction (optional): a function that takes two arguments and returns a boolean if the two arguments should be considered equal.
• objectA: an object or value
• objectA: another object or value to be compared with objectA

Return Value

objEql() returns true if either both objects have the same identity, or if both have the same attributes and all attribute comparisons return true (=== by default). Otherwise, objEql() returns false.

Custom comparison functions

By default === is used to check equality of each value. An optional comparson may be supplied instead. The comparison function is supplied as the first argument because parital application is a thing.

ImmutableJS

If the object contains ImmutableJS values, Immutable.is can be used directly as the comparion function.

var Immutable = require('immutable')
objEql(Immutable.is, a, b)

Since mutating an ImmutableJS value always returns a reference to itself it there was no change, === (the objEql default) can be used to test for changes. However, for testing if two cases resulted in the same Immutable value, Immutable.is can identify the values as being equal.

Deep Equality

By binding objEql with itself as a comparison function it is even possible to support deep equality checking.

var objEqlDeep = objEql.bind(null, (a, b) => objEqlDeep(a, b))

This may seen like a novel trick; however, in my limited tests, this out performs deep-equal every time. If you need to do deep equality testing you should seriously consider using a persistent data structure implementation like ImmutableJS. It will be much faster.

Since this could be a common use case, obj-eql exposes a pre-bound deep equality function as objEql.deep(a, b). It is implimented in one line exactly as seen above.