Immutable.js provides several conversion methods to migrate one structure to another. Each Immutable.js class contains a prefixed "to" method like Map.toList(), Map.toSet(), etc. Converting these types sometimes results in a loss of data, as we will see when converting from Map to List.

 

Map to List:

it('should convert Map() to List()', () => {    const map = Immutable.Map({      key1: 'First Item',       key2: 'Second Item'    });        const convertedList = map.toList();        expect(Immutable.List.isList(convertedList)).to.be.true;        // Keys are discarded    expect(convertedList.first()).to.equal('First Item');    expect(convertedList.last()).to.equal('Second Item');      });

 

List to Map:

it('should convert List() to Map()', () => {    const list = Immutable.List.of('First Item', 'Second Item');        const convertedMap = list.toMap();        // Converted keys ascend numerically    keys = convertedMap.keys();    expect(keys.next().value).to.equal(0);    expect(keys.next().value).to.equal(1);        expect(Immutable.Map.isMap(convertedMap)).to.be.true;        expect(convertedMap.first()).to.equal('First Item');    expect(convertedMap.last()).to.equal('Second Item');      });

 

Map to Javascript Array:

it('should convert Map() to Javascript Array', () => {    const map = Immutable.Map({      key1: 'First Item',       key2: 'Second Item',      key3: {key4: 'Nested Item'}    });        const arr = map.toArray();        // Keys are discarded    expect(arr[0]).to.equal('First Item');    expect(arr[1]).to.equal('Second Item');    expect(arr[2].key4).to.equal('Nested Item');      });

 

Map to JSON:

it('should convert Map() to JSON', () => {    const map = Immutable.Map({      key1: 'First Item',       key2: 'Second Item',      key3: {key4: 'Nested Item'}    });        const json = map.toJSON();        expect(json.key1).to.equal('First Item');    expect(json.key2).to.equal('Second Item');    expect(json.key3.key4).to.equal('Nested Item');      });