ES6 Basics

1/25 The statement "let" declares a block scope local variable.
- 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 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.
4/25 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.
5/25 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
6/25 What will the result of this expression be?
```
typeof (new (class F extends (String, Array) { })).substring
```
- Error
- "undefined"
- "object"
- "function"
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 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.
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 Which ES6 feature provides a new way to handle asynchronous operations?
- Callbacks
- Promises
- Async/Await
- Event Listeners
12/25 What does the 'Set' object introduced in ES6 represent?
- A collection of unique values
- A key-value map
- A sequential list of elements
- A set of functions
13/25 Which of the following is a template literal in ES6?
- 'Hello World'
- `Hello ${name}`
- "Hello " + name
- Hello + name
14/25 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
15/25 In ES6, which syntax is used for defining a class?
- function MyClass() {}
- class MyClass {}
- MyClass = new Class()
- object MyClass {}
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 How does the 'for...of' loop in ES6 differ from 'for...in'?
- for...of iterates over properties
- for...of is used for objects
- for...of iterates over iterable objects like arrays
- There is no difference
19/25 In ES6, what is the main use of a 'Symbol'?
- To create unique, immutable identifiers
- To symbolize constants
- To enhance security
- To replace strings
20/25 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 {}
21/25 Which method in ES6 is used to copy an object?
- Object.copy()
- Object.clone()
- Object.assign()
- Object.duplicate()
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 is the result of using a template literal inside another template literal?
- Syntax error
- The inner template literal is ignored
- Nested template processing
- Automatic string conversion
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
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ES6 Basics

1/25 The statement "let" declares a block scope local variable.

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

3/25 What will the result of the following be?

4/25 String interpolation is a much-needed new feature that is finally available in JavaScript. See the example below. Is there anything wrong with it?

5/25 What will this function return?

6/25 What will the result of this expression be?

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

10/25 What is stored in the triangle array?

11/25 Which ES6 feature provides a new way to handle asynchronous operations?

12/25 What does the 'Set' object introduced in ES6 represent?

13/25 Which of the following is a template literal in ES6?

14/25 What is the output of the following code snippet? `const [a, , b] = [1, 2, 3]; console.log(a, b);`

15/25 In ES6, which syntax is used for defining a class?

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

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

18/25 How does the 'for...of' loop in ES6 differ from 'for...in'?

19/25 In ES6, what is the main use of a 'Symbol'?

20/25 In ES6, which statement correctly creates a class that extends another class?

21/25 Which method in ES6 is used to copy an object?

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 is the result of using a template literal inside another template literal?

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