objects | create | clone | get attributes subset | destructuring

src.js

> [{a:1}, {b:2}, {c:3}].reduce((acc, o) => {return Object.assign(acc, o)}, {})
{a: 1, b: 2, c: 3}

> e = {a: 1}
> e = {...e, b: 1}
{a: 1, b: 2}

// Creating object attributes with names of array elements
> arr = ['a', 'b', 'c']
> Object.assign(...arr.map((attr, index) => {return {[attr]: index}}), {})
{a: 0, b: 1, c: 2}

// Destructuring assignement:
// Unpack values from arrays, or properties from objects, into distinct variables
> (({ a, c }) => ({ a, c }))({'a': 0, 'b': 1, 'c': 2}) 
{a: 0, c: 2}

// CLONING
> A = {a: 1}
> B = Object.assign({}, a)
> A.a = 0
> B.a
1

// All arrays are objects, checking the constructor property is fast for JavaScript engines
> arr = []
> arr.constructor === Array
true
> A = {arr: []}
> A.arr && A.arr.constructor === Array
true

> A = [1]
> B = A.slice()
> A[0] = 0
> B
[1]