Week of July 16 2018

Question 1

REACT:

What’s he name of the npm package for React Router

Answer 1

react-router-dom

Question 2

REACT ROUTER:

What to import from React Router to create basic routes.

Answer 2

BrowserRouter, Route

Question 3

REACT:

Conditional rendering inline. How to check if an array is empty?

Answer 3

array. length > 0 && ….(render component)

array. length alone will not work as this value has to be a true boolean (not just truthy or falsy)

Question 4

REACT:

When to use parentheses in React components returning JSX?

Answer 4

• Parentheses are needed when explicitly returning multiple lines of code (in general in JS) , i.e. when using the ‘return’ keyword.
• Parentheses are not needed when implicitly (no return keyword) returning JSX in arrow functions (even multiple lines).
• Some (including Prettify) consider wrapping multiple lines of JSX in parentheses - even in the latter case - best practice.

Question 5

JAVASCRIPT:
Explain ‘const’
(5 bullets)

Answer 5

• used to declare a constant
• values can only be assigned at time of declaration
• constants cannot be redeclared
• constants in JS are block scoped
• ES 2015 syntax

Question 6

JAVASCRIPT:

What does immutable mean in Javascript?

Answer 6

• Immutable data types cannot be changed after they were created.
• JS primitive data types are immutable: strings, numbers, booleans, null, undefined, symbol (new in ECMAScript 2015).
• Changing a value will create a new value.

https://benmccormick.org/2016/06/04/what-are-mutable-and-immutable-data-structures-2/

Question 7

JAVASCRIPT:

What does mutable mean in Javascript?

Answer 7

• Mutable data types are objects (including ES 2015 sets and maps).
• Changing a value will change the value in all references.

Question 8

JAVASCRIPT:

What’s a ES 2015 alternative for a for loop?

Answer 8

for…of:

creates a loop iterating over iterable objects (arrays, strings, etc.)

Question 9

REACT - Forms:

What’s the difference between HTML and JSX in “” elements of the type text?

Answer 9

None.

Question 10

REACT - Forms:

What’s the difference between HTML and JSX in elements?

Answer 10

HTML:
- text content goes in between tags.
Content goes here

JSX: text content is assigned in value prop (similarly to text input)

Question 11

REACT - Forms:

What’s the difference between HTML and JSX in dropdown elements and ?

Answer 11

Only difference is the by default selected option:

HTML (select by adding a select prop (no value)

One
Two
Three

JSX (select by setting select element’s value)

One
Two
Three

Question 12

REACT:
Way to satisfy React’s (or React Router’s) requirement to return a single parent element without adding another div to the DOM?

Answer 12

Wrap with

Question 13

INTERVIEWS:

What do interviewers likely want to learn when they ask you about projects?

Answer 13

Besides that they want you to be an active coder they want to see that you can articulate and describe technical issues. So go into implementation details!

Question 14

REACT:

How to direct with React Router?

Answer 14

Use withRouter function supplied by react-router-dom and return the component from the function (wrap it) which gives you the history.push method.