Think You Know ES6? Prove it!

The let Statement

ES6 gives us a "let" statement - a new way to declare variables. Can you guess what it does?

• It functions exactly like var.
• Introduces block scoping. Variables defined with let are available only in the nearest enclosing block.
• Always makes variables equal 150.

The const Statement

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

• Const turns variables into constants, and they can't be changed.
• It is used to define math-related variables.
• It is exactly the same as let.

Arrow Functions

Arrow functions work similarly to regular function, but are shorter to write. Can you guess what is the correct usage?

• A
• B
• None of these are correct.

New String Methods

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

• some_text.endsWith()
• some_text.repeat()
• some_text.includes()

New Array Methods

Did you know we have new array methods as well? Guess which one of them can help shorten this code?

• A
• B
• C

New Array Methods II

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

• You use it because it is hip.
• This code is wrong and won't work.
• You need it, because querySelectorAll returns a NodeList, which doesn't have the map method, only arrays do.

Default Parameters

What results will these function calls return?

• A - 15, B - 13, C - 30, D - 15
• A - 13, B - 8, C - 30, D - 15
• A - 13, B - 13, C - 30, D - undefined

Classes

Which language is this?

• Java
• JavaScript
• C#

Destructuring

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

• Create an array containing a and b.
• Make both a and b equal 12.
• Swap the values inside a and b, without using extra variables.

Object Declaration

What's the ES6 way for quick initialization of objects from variables?

• A
• B
• None of these are correct.

The Spread Operator

What is stored into the triangle array?

• [ [1,3], [5,5], [1,8] ]
• [1,3,5,5,1,8]
• 23

Rest parameters

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

• "a" becomes "1 23 4"
• "a" becomes [1,23,4]
• "a" is undefined

Template literal

String interpolation is a much-needed new feature that is finally available in JS. See an example below. Is there anything wrong with it?

• There is nothing wrong with it. This is how string interpolation works in ES6.
• This is wrong. You can't break a string into separate lines in JavaScript!
• This is wrong. You can't embed variables in strings in JavaScript!

New For Loops

ES6 comes with new, build in "for loops". Which one of them do we have to use to mimic the functionality of this traditional "for"?

• A
• B
• They do the same thing.

Object.assign

In the function below, what do we use Object.assign for?

• You use it to provide default parameters to the function, which users can override.
• Create a string containing 'defaults' and 'param'.
• Checks whether defaults equals param.

Promises

• Something you say when you want people to believe you.
• A tool for managing asynchronous control flow. A Promise represents an operation that is expected to complete in the future.
• The opposite of Amateurmise()

Generators and yield

Generators allow us to pause and resume the execution of a function*. What will be printed after running this code?

• -1
• 2
• 100

Great job!

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