Make the === operator compare arrays by values instead of references.

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101.0.77 years ago7 years agoMinified + gzip package size for equal-array in KB


Build Status Coverage Status License: MIT
equal-array lets the strict equality operator === compare arrays by values instead of references. Comparison can be either shallow or deeper.


It is mainly useful with an es6 Map or Set, because arrays, used as keys, are compared by references. For example :
const map = new Map();
map.set([1, 2 ,3], 'a');
map.set([1, 2 ,3], 'b'); // the map will consider [1, 2 ,3] as a new key
map.size; // returns 2 - with equal-array: returns 1
map.has([1, 2, 3]); // returns false - with equal-array: returns true


npm install equal-array


import EqualArray from 'equal-array';
// ES5: var EqualArray = require('equal-array').default;

const eq = new EqualArray();
// eq is a function

eq([1, 2, 3]) === eq([1, 2, 3]); //returns true

const map = new Map();
map.set(eq([1, 2 ,3]), 'a');
map.set(eq([1, 2 ,3]), 'b');
map.size; // returns 1
map.has(eq([1, 2, 3])); // returns true


const eq = new EqualArray({
 returnArray: false,
 conversion: true


accepted values: false (default) or true
If returnArray is true, the eq function returns a cloned array, otherwise a unique integer. The default is false to maximize performances.


accepted values: true (default), false, or a callback
Apply a conversion to the array elements in order to make the comparison. This is important if the array contains objects.
If conversion is false then :
eq([1, 2, new Date(1995, 10)]) !== eq([1, 2, new Date(1995, 10)])

If conversion is true then :
eq([1, 2, new Date(1995, 10)]) === eq([1, 2, new Date(1995, 10)])
Setting conversion to true means that EqualArray will call the valueOf() function on each element (when applicable).
The conversion option also accepts a callback which takes as a parameter an element of an array and returns the value to be compared:
const obj1 = {dummy: 1};
const obj2 = {dummy: 1};
const obj3 = {dummy: 99};
const callback = element => element.dummy;
const eq = new EqualArray({conversion: callback});
eq([obj1]) === eq([obj2]); // true
eq([obj1]) === eq([obj3]); // false