ES6 Basics

1/25 Constants are block-scoped variables.
- True
- False
2/25 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
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 is a Promise()?
- Tool for managing asynchronous control flow. A promise represents an operation expected to complete in the future.
- The opposite of Amateurmise().
- Something you say, when you want someone to believe you.
- None of the above.
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 ES6 gives you a number of new methods for operating with Strings. Which one replaces this annoying piece of code?
```
let some_text = "some string"; 

if(some_text.indexOf('str') !=-1){

 return true;

 }
```
- some_text.repeat('str');
- some_text.endsWith('str');
- some_text.includes('str');
9/25 ES6 gives an alternative way to assign variables. Can you guess what the below code does?
```
let a = 12, b = 3;

[a, b] = [b, a];
```
- Makes both a and b equal 12.
- Swaps the values inside a and b, without using extra variables.
- Creates an array that contains a and b.
10/25 What is stored in the triangle array?
```
let point = [1,3], segment = [point,[5,5]], triangle = [...segment,[1,8]];
```
- 23
- [1,3,5,5,1,8]
- [ [1,3], [5,5], [1,8] ]

11/25 Is this a valid code?

class Slave { // ... };

 const slave = Slave();

12/25 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
13/25 In ES6, which keyword is used to import modules?
- require
- import
- include
- load
14/25 Which of the following is a template literal in ES6?
- 'Hello World'
- `Hello ${name}`
- "Hello " + name
- Hello + name
15/25 What is the output of the following code snippet? `const [a, , b] = [1, 2, 3]; console.log(a, b);`
```
const [a, , b] = [1, 2, 3]; 

console.log(a, b);
```
- 1, 2
- 2, 3
- 1, 3
- undefined, undefined
16/25 What is the result of using '...' in function parameters?
- Spread Operator
- Rest Parameters
- Destructuring
- Array Concatenation
17/25 How does 'const' behave differently from 'var' in ES6?
- const variables can be reassigned
- const creates block-level scope
- const does not allow hoisting
- const is not compatible with older browsers
18/25 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
19/25 Which new data structure introduced in ES6 stores unique values of any type?
- Array
- Object
- Map
- Set
20/25 What feature in ES6 allows for default parameter values in functions?
- Default Assignment
- Parameter Initialization
- Default Parameters
- Optional Parameters
21/25 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
22/25 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 {}
23/25 In ES6, what is the purpose of 'WeakSet'?
- To store a weakly held set of unique values
- To create a set with weakened security
- To store a set of weak references
- To create a less efficient version of Set
24/25 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
25/25 What is the main feature of 'Async/Await' introduced in ES8 (ECMAScript 2017)?
- Synchronous programming
- Error handling
- Asynchronous programming
- Parallel processing
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ES6 Basics

1/25 Constants are block-scoped variables.

2/25 What is the final value of "obj" in the following example?

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 is a Promise()?

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 ES6 gives you a number of new methods for operating with Strings. Which one replaces this annoying piece of code?

9/25 ES6 gives an alternative way to assign variables. Can you guess what the below code does?

10/25 What is stored in the triangle array?

11/25 Is this a valid code?

12/25 Which statement about arrow functions in ES6 is true?

13/25 In ES6, which keyword is used to import modules?

14/25 Which of the following is a template literal in ES6?

15/25 What is the output of the following code snippet? `const [a, , b] = [1, 2, 3]; console.log(a, b);`

16/25 What is the result of using '...' in function parameters?

17/25 How does 'const' behave differently from 'var' in ES6?

18/25 What is the main advantage of using 'let' over 'var' in ES6?

19/25 Which new data structure introduced in ES6 stores unique values of any type?

20/25 What feature in ES6 allows for default parameter values in functions?

21/25 What is a 'Proxy' in ES6?

22/25 In ES6, which statement correctly creates a class that extends another class?

23/25 In ES6, what is the purpose of 'WeakSet'?

24/25 How does 'yield' work in ES6?

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