array-concatenation.js

const arr1 = ["a","b","c"];
const arr2 = ["d","e","f"];
const arr3 = ["g","h","i"];


// Array.prototype.concat()
const arrayConcat = arr1.concat(arr2).concat(arr3);

// Array.prototype.push() + spread operator
const arrayPush = [];
arrayPush.push(...arr1, ...arr2, ...arr3);

// Array constructor + spread operator
const arrayConstructor = Array(...arr1, ...arr2, ...arr3);

// Array constructor + Array.prototype.flat()
const flatArrayConstructor = Array(arr1, arr2, arr3).flat();

// Array.of + spread operator
const arrayOf = Array.of(...arr1, ...arr2, ...arr3);

// Array.of + Array.prototype.flat
const flatArrayOf = Array.of(arr1, arr2, arr3).flat();

// Spread Operator
const arraySpread = [...arr1, ...arr2, ...arr3];

// Array.prototype.flat
const flatArraySpread = [arr1, arr2, arr3].flat();


console.log({
  arrayConcat,
  arrayPush,
  arrayConstructor,
  flatArrayConstructor,
  arrayOf,
  flatArrayOf,
  arraySpread,
  flatArraySpread
});
// {arrayConcat: Array(9), arrayPush: Array(9), arrayConstructor: Array(9), flatArrayConstructor: Array(9), arrayOf: Array(9), …}
// arrayConcat: (9) ["a", "b", "c", "d", "e", "f", "g", "h", "i"]
// arrayConstructor: (9) ["a", "b", "c", "d", "e", "f", "g", "h", "i"]
// arrayOf: (9) ["a", "b", "c", "d", "e", "f", "g", "h", "i"]
// arrayPush: (9) ["a", "b", "c", "d", "e", "f", "g", "h", "i"]
// arraySpread: (9) ["a", "b", "c", "d", "e", "f", "g", "h", "i"]
// flatArrayConstructor: (9) ["a", "b", "c", "d", "e", "f", "g", "h", "i"]
// flatArrayOf: (9) ["a", "b", "c", "d", "e", "f", "g", "h", "i"]
// flatArraySpread: (9) ["a", "b", "c", "d", "e", "f", "g", "h", "i"]


// proof of immutability
console.log({
  arr1,
  arr2,
  arr3
});
// {arr1: Array(3), arr2: Array(3), arr3: Array(3)}
// arr1: (3) ["a", "b", "c"]
// arr2: (3) ["d", "e", "f"]
// arr3: (3) ["g", "h", "i"]