JAVASCRIPT

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"

How to Destructuring Array in Javascript?

//destructuring array 
const alphabet = ['a', 'b', 'c', 'b', 'e'];
const [a, b] = alphabet;
console.log(a, b);
//Expected output: a b

Array destructuring JS

// In an array destructuring from an array of length N specified on the right-hand side of the assignment, if the number of variables specified on the left-hand side of the assignment is greater than N, only the first N variables are assigned values. The values of the remaining variables will be undefined.

const foo = ['one', 'two'];

const [red, yellow, green, blue] = foo;
console.log(red); // "one"
console.log(yellow); // "two"
console.log(green); // undefined
console.log(blue);  //undefined

javascript destructuring

const [a, b] = array;
const [a, , b] = array;
const [a = aDefault, b] = array;
const [a, b, ...rest] = array;
const [a, , b, ...rest] = array;
const [a, b, ...{ pop, push }] = array;
const [a, b, ...[c, d]] = array;

const { a, b } = obj;
const { a: a1, b: b1 } = obj;
const { a: a1 = aDefault, b = bDefault } = obj;
const { a, b, ...rest } = obj;
const { a: a1, b: b1, ...rest } = obj;

let a, b, a1, b1, c, d, rest, pop, push;
[a, b] = array;
[a, , b] = array;
[a = aDefault, b] = array;
[a, b, ...rest] = array;
[a, , b, ...rest] = array;
[a, b, ...{ pop, push }] = array;
[a, b, ...[c, d]] = array;

({ a, b } = obj); // brackets are required
({ a: a1, b: b1 } = obj);
({ a: a1 = aDefault, b = bDefault } = obj);
({ a, b, ...rest } = obj);
({ a: a1, b: b1, ...rest } = obj);

Destructuring in ES6

var a = obj.a
var b = obj.b
var c = obj.c

javascript default parameters object destructuring

You can use "defaults" in destructuring as well:

(function test({a = "foo", b = "bar"} = {}) {
  console.log(a + " " + b);
})();

This is not restricted to function parameters, 
but works in every destructuring expression.

javascript function destructuring

// destructuring assignment when passing
// an object of properties to a function
function example({userOptions: {query, all = true, sort} = {}, array}) {
  console.log(query, all, sort) // something false ascending
}

// for clarity, the above example is destructured the same as this
function example({userOptions, array}){
  const {query, all = true, sort} = userOptions || {}
}

const userOptions = {query: 'something', all: false, sort: 'ascending'}
const array = []
example({userOptions, array})

Array Destructuring

const foo = ['one', 'two', 'three'];

const [red, yellow, green] = foo;
console.log(red); // "one"
console.log(yellow); // "two"
console.log(green); // "three"

js destructuring

let [person, age] = ['John', 26]
let msg = `${person} is ${age} years old`
console.log(msg)

Javascript array destructuring

let [a, b] = [9, 5]
[b, a] = [a, b]
console.log(a, b);
//Expected output: 5,9

javascript Array Destructuring

const arrValue = ['one', 'two', 'three'];

// destructuring assignment in arrays
const [x, y, z] = arrValue;

console.log(x); // one
console.log(y); // two
console.log(z); // three

JavaScript Destructuring - From ES6

// assigning object attributes to variables
const person = {
    name: 'Sara',
    age: 25,
    gender: 'female'    
}

// destructuring assignment
let { name, age, gender } = person;

console.log(name); // Sara
console.log(age); // 25
console.log(gender); // female

object destructuring example

const hero = {
  name: 'Batman',
  realName: 'Bruce Wayne',
  address: {
    city: 'Gotham'
  }
};

// Object destructuring:
const { realName, address: { city } } = hero;
city; // => 'Gotham'

destructuring in javascript

/*
Array Destructuring: The following example shows us how to convert all 
the elements of an array to a variable.

Object Destructuring: The following example shows us how to convert all 
the properties of an object into a variable.
*/
//Array Destructuring
const friends = ['Bill', 'Gates'];
const [firstName, secondName] = friends;
console.log(secondName);  //Gates

//Object Destructuring
const person = {name: "Bill Gates", age: 17, phone: "123456789"};
const {name} = person;
console.log(name);  //Bill Gates

Destructuring of array in ES6

function printFirstAndSecondElement([first, second]) {
    console.log('First element is ' + first + ', second is ' + second)
}

function printSecondAndFourthElement([, second, , fourth]) {
    console.log('Second element is ' + second + ', fourth is ' + fourth)
}

var array = [1, 2, 3, 4, 5]

printFirstAndSecondElement(array)
printSecondAndFourthElement(array)

JavaScript Destructuring

// before you would do something like this
const person = {
    name: 'Sara',
    age: 25,
    gender: 'female'    
}

let name = person.name;
let age = person.age;
let gender = person.gender;

console.log(name); // Sara
console.log(age); // 25
console.log(gender); // female

js object destructuring with defaults

// Taken from top stack overflow answer

const { dogName = 'snickers' } = { dogName: undefined }
console.log(dogName) // what will it be? 'snickers'!

const { dogName = 'snickers' } = { dogName: null }
console.log(dogName) // what will it be? null!

const { dogName = 'snickers' } = { dogName: false }
console.log(dogName) // what will it be? false!

const { dogName = 'snickers' } = { dogName: 0 }
console.log(dogName) // what will it be? 0!

destructuring an array

let cars = ['ferrari', 'tesla', 'cadillac'];
let [car1, car2, car3] = cars;
console.log(car1, car2, car3); // Prints: ferrari tesla cadillac

js-destructuring

const getTemperature = ({ celsius = 15 } = {}) => celsius;

Destructuring in ES6

let {a, b, c} = obj

javascript function destructuring

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

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

destructuring javascript

let a, b, rest;
[a, b] = [10, 20];
console.log(a); // 10
console.log(b); // 20

[a, b, ...rest] = [10, 20, 30, 40, 50];
console.log(a); // 10
console.log(b); // 20
console.log(rest); // [30, 40, 50]

({ a, b } = { a: 10, b: 20 });
console.log(a); // 10
console.log(b); // 20

// Stage 4(finished) proposal
({a, b, ...rest} = {a: 10, b: 20, c: 30, d: 40});
console.log(a); // 10
console.log(b); // 20
console.log(rest); // {c: 30, d: 40}

js destructuring explained

const { identifier } = expression;

js-destructuring

const getTemperature = (atticData) => atticData?.celsius ?? 15;
// insted do
const getTemperature = ({ celsius = 15 } = {}) => celsius;

// https://realworldjs.medium.com/never-use-the-dot-operator-in-javascript-ee0339d85fb

Destructuring assignment JS

const [firstElement, secondElement] = list;
// is equivalent to:
// const firstElement = list[0];
// const secondElement = list[1];

// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment

array destructuring in js

const arr = [1, 2, 3, 4];
const [first, second] = arr; // first = 1, second = 2

js Destructuring arguments

const circle = {
  label: 'circleX',
  radius: 2,
};

const circleArea = ({ radius }, [precision = 2]) =>
  (Math.PI * radius * radius).toFixed(precision);

console.log(
  circleArea(circle, [5]) // 12.56637
);

JavaScript Destructuring - Before ES6

// assigning object attributes to variables
const person = {
    name: 'Sara',
    age: 25,
    gender: 'female'    
}

let name = person.name;
let age = person.age;
let gender = person.gender;

console.log(name); // Sara
console.log(age); // 25
console.log(gender); // female

destructuring array ES6

let a = 8, b = 6;
[a, b] = [b, a];

Array destructuring

let [name, team] = ["Bob", "100Devs"]

console.log(name)//"Bob"
console.log(team)//"100Devs"

js destructuring

/*simple example*/
const [name, age] = ["malek","25"];

Destructuring in javascript

const { name, age, job } = { name: 'abrar', age: 24, job: 'web-developer' }
console.log(name, age, job)

js destructuring

function calculatefood (food, tip) {
    tip_percent = tip / 100;
    tip_amount = food * tip_percent;
    total = food + tip_amount;
    return [tip_amount, total];
}
const [tip, sum] = calculatefood(100, 20);
console.log(tip);
console.log(sum);

destructuring assignment in javascript

// destructuring assignment in javascript
// object destructuring
let person = { 
    name: "Chetan", 
    age: 30, 
    country: "India" 
};
const { name, age } = person;

console.log(name);
//expected output: "Chetan"

console.log(age);
//expected output: 30

console.log(country);
//expected output: Uncaught ReferenceError: country is not defined

// Array destructuring
const num = [1,2,3];
const [one, two, three] = num;
console.log(one); // 1
console.log(two); // 2
console.log(three); // 3