javascript destructuring arrays code example

Example 1: Destructuring Assignment

const HIGH_TEMPERATURES = {
  yesterday: 75,
  today: 77,
  tomorrow: 80
};

//ES6 assignment syntax
const {today, tomorrow} = HIGH_TEMPERATURES;

//ES5 assignment syntax
const today = HIGH_TEMPERATURES.today;
const tomorrow = HIGH_TEMPERATURES.tomorrow;

console.log(today); // 77
console.log(tomorrow); // 80
console.log(yesterday); // "ReferenceError: yesterday is not defined" as it should be.

Example 2: array destructuring

//Without destructuring

const myArray = ["a", "b", "c"];

const x = myArray[0];
const y = myArray[1];

console.log(x, y); // "a" "b"

//With destructuring

const myArray = ["a", "b", "c"];

const [x, y] = myArray; // That's it !

console.log(x, y); // "a" "b"

Example 3: destructuring assignment

Destructuring assignment is special syntax introduced in ES6, 
for neatly assigning values taken directly from an object.

const user = { name: 'John Doe', age: 34 };

const { name, age } = user;
// name = 'John Doe', age = 34

Example 4: javascript function destructuring

function f() {
  return [1, 2];
}

let a, b; 
[a, b] = f(); 
console.log(a); // 1
console.log(b); // 2

Example 5: javascript destructing

/*
* On the left-hand side, you decide which values to unpack from the right-hand
* side source variable.
* 
* This was introduced in ES6
*/
const x = [1, 2, 3, 4, 5]
const [a, b] = x
console.log(a) // prints out: 1
console.log(b) // prints out: 2

Example 6: mdn destructuring

let a, b;

[a, b] = [1, 2];
console.log(a); // 1
console.log(b); // 2