ES6 Basics

1/25 Constants are block-scoped variables.
- True
- False
2/25 Rest is a new way for functions to handle an arbitrary number of parameters. Can you guess what the mysterious "a" variable holds?
```
function mystery(...params) {

  return params; 

}

let a = mystery(1,23,4);
```
- "a" is undefined
- "a" becomes [1,23,4]
- "a" becomes "1 23 4"
- "a" becomes 1 23 4
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 value will this expression return?
```
let x, { x: y = 1 } = { x };   y;
```
- { x: 1 }
- 1
- { x : 1 }
- "undefined"
5/25 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.

6/25 What will this function return?

(function() { 

if (false) {

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

 }

 return typeof f;

 })()

Undefined
"object"
"function"
Error

7/25 What result will this expression have?
```
typeof (function* f() { yield f })().next().next()
```
- "generator"
- "object"
- "function"
- Error
8/25 Why is super used?
- Is used for creating and initializing an object.
- It's a simple function.
- Is used as an "object" which calls the parent class.
- Is used as a "function" which calls the parent's constructor.
9/25 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.
10/25 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.
11/25 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] ]

12/25 Is this a valid code?

class Slave { // ... };

 const slave = Slave();

13/25 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
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 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
17/25 Which new data structure introduced in ES6 stores unique values of any type?
- Array
- Object
- Map
- Set
18/25 What feature in ES6 allows for default parameter values in functions?
- Default Assignment
- Parameter Initialization
- Default Parameters
- Optional Parameters
19/25 What ES6 feature provides a shorthand syntax for assigning properties to variables of the same name?
- Property Shorthand
- Object Destructuring
- Variable Initialization
- Arrow Functions
20/25 Which method in ES6 is used to copy an object?
- Object.copy()
- Object.clone()
- Object.assign()
- Object.duplicate()
21/25 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
22/25 What is the main feature of 'Async/Await' introduced in ES8 (ECMAScript 2017)?
- Synchronous programming
- Error handling
- Asynchronous programming
- Parallel processing
23/25 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
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
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ES6 Basics

1/25 Constants are block-scoped variables.

2/25 Rest is a new way for functions to handle an arbitrary number of parameters. Can you guess what the mysterious "a" variable holds?

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 value will this expression return?

5/25 What is a Promise()?

6/25 What will this function return?

7/25 What result will this expression have?

8/25 Why is super used?

9/25 ES6 introduces a special "const" declaration. Do you know what it does?

10/25 Array.from() is a powerful method which converts array-like objects into real Arrays. Why do you use it in the code below?

11/25 What is stored in the triangle array?

12/25 Is this a valid code?

13/25 What does the 'Set' object introduced in ES6 represent?

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 main advantage of using 'let' over 'var' in ES6?

17/25 Which new data structure introduced in ES6 stores unique values of any type?

18/25 What feature in ES6 allows for default parameter values in functions?

19/25 What ES6 feature provides a shorthand syntax for assigning properties to variables of the same name?

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

21/25 In ES6, what is the purpose of 'WeakSet'?

22/25 What is the main feature of 'Async/Await' introduced in ES8 (ECMAScript 2017)?

23/25 In ES6, what is the result of using a template literal inside another template literal?

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

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