Destructuring in ES6 Flashcards

Question 1

Q

What is Destructuring in JavaScript?

Answer

A

Destructuring in JavaScript is a simplified method of extracting multiple properties from an array by taking the structure and deconstructing it down into its own constituent parts through assignments by using a syntax that looks similar to array literals.

var [first, second, third] = [“Laide”, “Gabriel”, “Jets”];

Question 2

Q

Can you use number for desctructuring?

Answer

A

You cannot use Numbers for destructuring. Numbers will throw an error because numbers cannot be variable names.

Question 3

Q

Can declaration and assignment can be done separately in destructuring?

Answer

A

Declaration and assignment can be done separately in destructuring.

Question 4

Q

var things = [“Table”, “Chair”, “Fan”, “Rug”];
var [a, b, c, d, e] = things;

console.log(c); //Output:
console.log(d); //Output:
console.log(e); //Output:

Answer

A

console.log(c); //Output: Fan
console.log(d); //Output: Rug
console.log(e); //Output: undefined

Question 5

Q

var things = [“Table”, “Chair”, “Fan”, “Rug”];
var [a, b, c] = things;
console.log(c);

Answer

A

Output: Fan

Question 6

Q

var a, b;
[a = 40, b = 4] = [];
console.log(a);
console.log(b);

Answer

A

var a, b;
[a = 40, b = 4] = [];
console.log(a); //Output: 40
console.log(b); //Output: 4

Question 7

Q

[a = 40, b = 4] = [1, 23];
console.log(a);
console.log(b);

Answer

A

[a = 40, b = 4] = [1, 23];
console.log(a); //Output: 1
console.log(b); //Output: 23

Question 8

Q

var [first = “Cotlin”, second = first] = [];
console.log(first);
console.log(second);

Answer

A

var [first = “Cotlin”, second = first] = [];
console.log(first); //Output: Cotlin
console.log(second); //Output: Cotlin

Question 9

Q

var [first = “Cotlin”, second = first] = [“Koku”];
console.log(first);
console.log(second);

Answer

A

var [first = “Cotlin”, second = first] = [“Koku”];
console.log(first); //Output: Koku
console.log(second); //Output: Koku

Question 10

Q

var [first = “Cotlin”, second = first] = [“Koku”, “Lydia”];
console.log(first);
console.log(second);

Answer

A

var [first = “Cotlin”, second = first] = [“Koku”, “Lydia”];
console.log(first); //Output: Koku
console.log(second); //Output: Lydia

Question 11

Q

Destructuring lets you map a variable to the elements you are interested in. How can you ignore or skip other elements in the array?

Answer

A

You can ignore or skip the other elements in the array by using trailing commas.

Question 12

Q

var a, b;
[a, , b] = [“Lordy”, “Crown”, “Roses”];

console.log(a);
console.log(b);

Answer

A

var a, b;
[a, , b] = [“Lordy”, “Crown”, “Roses”];

console.log(a); //Output: Lordy
console.log(b); //Output: Roses

Question 13

Q

What is a Rest parameter used for?

Answer

A

A Rest parameter is used to map all the remaining elements in the array that have not been mapped to the rest variable itself.

Question 14

Q

var planets = [“Mercury”, “Earth”, “Venus”, “Mars”, “Pluto”, “Saturn”];
var [first, , third, …others] = planets;

console.log(first);
console.log(third);
console.log(others);

Answer

A

var planets = [“Mercury”, “Earth”, “Venus”, “Mars”, “Pluto”, “Saturn”];
var [first, , third, …others] = planets;

console.log(first); //Output: Mercury
console.log(third); //Output: Venus
console.log(others); //Output: [“Mars”, “Pluto”, “Saturn”]

Question 15

Q

If the (…) operator appears on the right-hand in destructuring then it is called a?

Answer

A

If the (…) operator appears on the right-hand in destructuring then it is a SPREAD SYNTAX

Question 16

Q