ES6 Basics

1/25 What is the final value of "obj" in the following example?
```
const obj = { foo: 1 }; 

obj.bar = 2;
```
- { foo: 1 }
- { foo: 1, bar: 2 }
- { foo: 1, 2: bar }
- None of the above
2/25 What will the result of the following be?
```
const speed = 'quick'; `The ${speed} brown fox jumps over the lazy dog.`
```
- SyntaxError
- "The speed brown fox jumps over the lazy dog."
- "The quick brown fox jumps over the lazy dog."
- Undefined
- The `quick` brown fox jumps over the lazy dog.
3/25 String interpolation is a much-needed new feature that is finally available in JavaScript. See the example below. Is there anything wrong with it?
```
let name = 'Harry';

let occupation = 'wizard';

console.log(`Hi! My name is ${name}. I'm a ${occupation}.`);
```
- Nothing wrong with the example. This is how the feature works in ES6.
- The example is wrong. You can't break a String into lines in JavaScript.
- The example is wrong. You can't embed variables in String in JavaScript.
- None of the above.
4/25 What will this function return?
```
(function() {

 let f = this ? class g { } : class h { };

 return [ typeof f, typeof h ];

 })();
```
- ["undefined", "undefined"]
- ["function", "function"]
- ["function", "undefined"]
- Error
5/25 What will the result of this expression be?
```
typeof (new (class F extends (String, Array) { })).substring
```
- Error
- "undefined"
- "object"
- "function"

6/25 What will this function return?

(function() { 

if (false) {

 let f = { g() => 1 };

 }

 return typeof f;

 })()

Undefined
"object"
"function"
Error

7/25 ES6 introduces a special "const" declaration. Do you know what it does?
```
const PI = 3.14; 

console.log(PI) //Prints 3.14
```
- It is exactly the same as let.
- It is used to define math-related variables.
- Const turns variables into constants, and they can't be changed.
8/25 Array.from() is a powerful method which converts array-like objects into real Arrays. Why do you use it in the code below?
```
let titleElements = document.querySelectorAll('.article .title') let titles = Array.from(titleElements).map( t => t.textContent ); console.log(titles);
```
- This code is wrong and won't work.
- You use it because it is hip.
- You need it, because querySelectorAll returns a NodeList, which doesn't have the map method, and only arrays do.

9/25 Is this a valid code?

class Slave { // ... };

 const slave = Slave();

10/25 What is the main purpose of the spread operator in ES6?
- To spread objects into arrays
- To expand iterable objects into individual elements
- To combine multiple functions into one
- To spread arrays into objects
11/25 Which statement about arrow functions in ES6 is true?
- They do not have their own 'this' context
- They can be used as constructors
- They are not hoisted
- They have their own 'arguments' object
12/25 Which ES6 feature provides a new way to handle asynchronous operations?
- Callbacks
- Promises
- Async/Await
- Event Listeners
13/25 Which ES6 feature allows for declaring read-only named constants?
- let
- var
- const
- static
14/25 What is the main advantage of using 'let' over 'var' in ES6?
- let provides function scope
- let supports redeclaration in the same scope
- let provides block-level scope
- let improves performance
15/25 In ES6, which statement correctly imports a single export from a module?
- import { myExport }
- import myExport from 'module'
- require('module').myExport
- load myExport from 'module'
16/25 What is a 'Proxy' in ES6?
- A method for creating objects
- A way to handle asynchronous requests
- A type of function
- An object that wraps another object to control access to it
17/25 What ES6 feature provides a shorthand syntax for assigning properties to variables of the same name?
- Property Shorthand
- Object Destructuring
- Variable Initialization
- Arrow Functions
18/25 What does the 'Map' object introduced in ES6 represent?
- A collection of key-value pairs
- A list of unique values
- A new way to create arrays
- A mapping function for arrays
19/25 In ES6, which statement correctly creates a class that extends another class?
- class SubClass extends BaseClass {}
- class SubClass inherits BaseClass {}
- SubClass.prototype = new BaseClass();
- class SubClass: BaseClass {}
20/25 Which method in ES6 is used to copy an object?
- Object.copy()
- Object.clone()
- Object.assign()
- Object.duplicate()
21/25 What does the 'find' method do on an array in ES6?
- Finds and replaces elements
- Finds the first element satisfying a condition
- Finds all elements that match a condition
- Sorts the array
22/25 How does 'yield' work in ES6?
- It pauses and resumes a generator function
- It yields control to another function
- It produces a value from a sequence
- It generates random values
23/25 What is the main feature of 'Async/Await' introduced in ES8 (ECMAScript 2017)?
- Synchronous programming
- Error handling
- Asynchronous programming
- Parallel processing
24/25 In ES6, what does 'Object.is()' do?
- Checks if two values are the same value
- Checks if an object has a specific property
- Creates a new object
- Compares two objects deeply
25/25 How does the 'endsWith()' method work with ES6 strings?
- It checks if a string ends with a specified substring
- It appends a specified substring to the end of a string
- It removes the specified substring from the end of a string
- It capitalizes the final character of a string
To get the result of the quiz, please provide your email address (optional)..

It seems you haven't answered any questions yet. Please provide your answers to proceed.

ES6 Basics

1/25 What is the final value of "obj" in the following example?

2/25 What will the result of the following be?

3/25 String interpolation is a much-needed new feature that is finally available in JavaScript. See the example below. Is there anything wrong with it?

4/25 What will this function return?

5/25 What will the result of this expression be?

6/25 What will this function return?

7/25 ES6 introduces a special "const" declaration. Do you know what it does?

8/25 Array.from() is a powerful method which converts array-like objects into real Arrays. Why do you use it in the code below?

9/25 Is this a valid code?

10/25 What is the main purpose of the spread operator in ES6?

11/25 Which statement about arrow functions in ES6 is true?

12/25 Which ES6 feature provides a new way to handle asynchronous operations?

13/25 Which ES6 feature allows for declaring read-only named constants?

14/25 What is the main advantage of using 'let' over 'var' in ES6?

15/25 In ES6, which statement correctly imports a single export from a module?

16/25 What is a 'Proxy' in ES6?

17/25 What ES6 feature provides a shorthand syntax for assigning properties to variables of the same name?

18/25 What does the 'Map' object introduced in ES6 represent?

19/25 In ES6, which statement correctly creates a class that extends another class?

20/25 Which method in ES6 is used to copy an object?

21/25 What does the 'find' method do on an array in ES6?

22/25 How does 'yield' work in ES6?

23/25 What is the main feature of 'Async/Await' introduced in ES8 (ECMAScript 2017)?

24/25 In ES6, what does 'Object.is()' do?

25/25 How does the 'endsWith()' method work with ES6 strings?