К содержанию

Spread operator and array merging in JavaScript

Let's say we have two arrays:

javascriptlet arr1 = ['a', 'b', 'c'];
let arr2 = [1, 2, 3];

Let's make sure that the elements of the array arr1 are inserted between the first and second elements of the array arr2.

In other words, we want to write code that will make the following array from the current array arr2:

javascript[1, 'a', 'b', 'c', 2, 3]

The problem, in general, can be solved through the splice method. However, this task is much easier to solve through spread:

javascriptlet arr1 = ['a', 'b', 'c'];
let arr2 = [1, ...arr1, 2, 3];

console.log(arr2); // shows [1, 'a', 'b', 'c', 2, 3]

Задание 1

Without running the code, determine what will be output to the console:

javascriptlet arr1 = [1, 2, 3];
let arr2 = [4, 5, 6];

let arr  = ['a', ...arr1, 'b', 'c', ...arr2];
console.log(arr);

Задание 2

Without running the code, determine what will be output to the console:

javascriptlet arr1 = [1, 2, 3];
let arr2 = [4, 5, 6];

let arr  = ['a', ...arr1, ...arr1, 'b', 'c'];
console.log(arr);

Задание 3

Without running the code, determine what will be output to the console:

javascriptlet arr1 = [1, 2, 3];
let arr2 = [...arr1, 4, 5, 6];

let arr  = ['a', 'b', 'c', ...arr2];
console.log(arr);

Задание 4

Without running the code, determine what will be output to the console:

javascriptlet arr1 = [1, 2, 3];
let arr2 = [...arr1, 4, 5, 6];
let arr3 = [...arr2, 7, 8, 9];

let arr  = [0, ...arr3];
console.log(arr);

Задание 5

Without running the code, determine what will be output to the console:

javascriptlet arr1 = [1, 2, 3];
let arr2 = [...arr1];

console.log(arr2);