ES6 Basics

1/25 Constants are block-scoped variables.
- True
- False
2/25 The statement "let" declares a block scope local variable.
- True
- False
3/25 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
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 value will this expression return?
```
[...[...'...']].length
```
- 3
- 6
- 9
- Error
6/25 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.
7/25 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.
8/25 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] ]
9/25 Which method introduced in ES6 is used to merge two or more arrays?
- Array.join()
- Array.concat()
- Array.merge()
- Array.combine()
10/25 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
11/25 In ES6, which keyword is used to import modules?
- require
- import
- include
- load
12/25 Which of the following is a template literal in ES6?
- 'Hello World'
- `Hello ${name}`
- "Hello " + name
- Hello + name
13/25 In ES6, which syntax is used for defining a class?
- function MyClass() {}
- class MyClass {}
- MyClass = new Class()
- object MyClass {}
14/25 Which ES6 feature is used to write expressions in a more concise way?
- Arrow Functions
- Template Literals
- Promises
- Destructuring Assignment
15/25 What is the result of using '...' in function parameters?
- Spread Operator
- Rest Parameters
- Destructuring
- Array Concatenation
16/25 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
17/25 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'
18/25 What feature in ES6 allows for default parameter values in functions?
- Default Assignment
- Parameter Initialization
- Default Parameters
- Optional Parameters
19/25 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
20/25 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
21/25 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 {}
22/25 Which method in ES6 is used to copy an object?
- Object.copy()
- Object.clone()
- Object.assign()
- Object.duplicate()
23/25 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
24/25 Which of the following is a new string method introduced in ES6?
- .contains()
- .includes()
- .findString()
- .hasText()
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 The statement "let" declares a block scope local variable.

3/25 What is the final value of "obj" in the following example?

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 value will this expression return?

6/25 ES6 introduces a special "const" declaration. Do you know what it does?

7/25 Array.from() is a powerful method which converts array-like objects into real Arrays. Why do you use it in the code below?

8/25 What is stored in the triangle array?

9/25 Which method introduced in ES6 is used to merge two or more arrays?

10/25 Which statement about arrow functions in ES6 is true?

11/25 In ES6, which keyword is used to import modules?

12/25 Which of the following is a template literal in ES6?

13/25 In ES6, which syntax is used for defining a class?

14/25 Which ES6 feature is used to write expressions in a more concise way?

15/25 What is the result of using '...' in function parameters?

16/25 How does 'const' behave differently from 'var' in ES6?

17/25 In ES6, which statement correctly imports a single export from a module?

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

19/25 How does the 'for...of' loop in ES6 differ from 'for...in'?

20/25 What does the 'Map' object introduced in ES6 represent?

21/25 In ES6, which statement correctly creates a class that extends another class?

22/25 Which method in ES6 is used to copy an object?

23/25 What does the 'find' method do on an array in ES6?

24/25 Which of the following is a new string method introduced in ES6?

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