unpacking javascript 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: js object destructuring

const { [propName]: identifier } = expression;