Object.fromEntries() converts key-value pairs (entries) into an object
fromEntries() method is defined on Object (not on the object literal)
const fn = {}.fromEntries;
assert.equal(typeof fn, 'function');
GIVEN a list of entries (a key and a value) each WILL be converted into an object
WHERE an entry is an array with two elements
const entry1 = ['key', 'value'];
assert.deepEqual(Object.fromEntries([entry1, entry2]), {key: 'value', key1: 'value 1'});
WHEN using arr.entries() the array-index becomes the key and values stay values
const arr = ['two', 'one'];
assert.deepEqual(Object.fromEntries(arr.entries()), {0: 'one', 1: 'two'});
WHERE an entry is a Map, and key and value map naturally
const map = new Map();
map.set('value', 'key');
map.set('value 1', 'key1');
assert.deepEqual(Object.fromEntries(map.entries()), {key: 'value', key1: 'value 1'});
WHERE an entry is a Set, the values are used as keys too
const set = new Set();
set.add('___');
assert.deepEqual(Object.fromEntries(set.entries()), {'set value 1': 'set value 1'});
WHERE an entry is an object, the properties 0 and 1 are key and value
const entry1Object = {1: 'key', 2: 'value'};
const entry2Object = {'key1': 'value 1'};
assert.deepEqual(Object.fromEntries([entry1Object, entry2Object]), {key: 'value', key1: 'value 1'});
Links
mdn
docs
Description of Object.fromEntries() on MDN.