Reference Comparison Immutable vs. Native

test.js

const { Map, List } = require('immutable');

const mapBeforeI = Map({ a: 1, b: List([1, 2]) });

// First let's experiment with an Immutable structure
// Perform set operation, but make the values the same
const mapAfterI = mapBeforeI.set('a', 1);
console.log(mapBeforeI === mapAfterI); // true

// Perform set operation, but make the values different
const mapAfterI2 = mapBeforeI.set('a', 2);
console.log(mapBeforeI === mapAfterI2); // false

// Perform deep set operation, but make the nested values the same
const mapAfterI3 = mapBeforeI.setIn(['b', 0], 1);
console.log(mapBeforeI === mapAfterI3); // true

// Perform deep set operation, but make the nested values different
const mapAfterI4 = mapBeforeI.setIn(['b', 0], 2);
console.log(mapBeforeI === mapAfterI4); // false

// Ok, works as expected!

// Now let's experiment with a native javascript structure
let mapBeforeN = { a: 1, b: [1, 2] };
const mapBeforeN2 = mapBeforeN;
// Reference is shared
console.log(mapBeforeN === mapBeforeN2); // true

// Don't change anything, but create a new reference by copying
const mapAfterN = Object.assign({}, mapBeforeN);
// Even though the values remain the same, the triple equals
// compares the references which are different
console.log(mapBeforeN === mapAfterN); // false

// Now, the values still remain the same, but references are
// again changed
const mapAfterN2 = Object.assign({}, mapBeforeN, { a: 1 });
console.log(mapBeforeN === mapAfterN2); // false

// Now, create a new reference, but assign the same values
mapBeforeN = { a: 1, b: [1, 2] };
// Reference is changed
console.log(mapBeforeN === mapBeforeN2); // false