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 value will this expression return?
```
let x, { x: y = 1 } = { x };   y;
```
- { x: 1 }
- 1
- { x : 1 }
- "undefined"
6/25 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
7/25 What will the result of this expression be?
```
typeof (new (class F extends (String, Array) { })).substring
```
- Error
- "undefined"
- "object"
- "function"
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 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 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
12/25 Which ES6 feature provides a new way to handle asynchronous operations?
- Callbacks
- Promises
- Async/Await
- Event Listeners
13/25 Which of the following is a template literal in ES6?
- 'Hello World'
- `Hello ${name}`
- "Hello " + name
- Hello + name
14/25 In ES6, which syntax is used for defining a class?
- function MyClass() {}
- class MyClass {}
- MyClass = new Class()
- object MyClass {}
15/25 Which ES6 feature is used to write expressions in a more concise way?
- Arrow Functions
- Template Literals
- Promises
- Destructuring Assignment
16/25 What is the result of using '...' in function parameters?
- Spread Operator
- Rest Parameters
- Destructuring
- Array Concatenation
17/25 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
18/25 What feature in ES6 allows for default parameter values in functions?
- Default Assignment
- Parameter Initialization
- Default Parameters
- Optional Parameters
19/25 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
20/25 In ES6, what is the main use of a 'Symbol'?
- To create unique, immutable identifiers
- To symbolize constants
- To enhance security
- To replace strings
21/25 Which method in ES6 is used to copy an object?
- Object.copy()
- Object.clone()
- Object.assign()
- Object.duplicate()
22/25 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
23/25 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
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 value will this expression return?

6/25 What will this function return?

7/25 What will the result of this expression be?

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 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 What is the main purpose of the spread operator in ES6?

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

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

14/25 In ES6, which syntax is used for defining a class?

15/25 Which ES6 feature is used to write expressions in a more concise way?

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

17/25 What is the main advantage of using 'let' over 'var' in ES6?

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

19/25 What is a 'Proxy' in ES6?

20/25 In ES6, what is the main use of a 'Symbol'?

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

22/25 What does the 'find' method do on an array in ES6?

23/25 How does 'yield' work in ES6?

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?