React

Question 1

What is React?

Answer 1

javascript framework for building composable UIs

Question 2

What are some features of React?

Answer 2

• JSX: ui language that allows us to write html inside of JS
• virtual DOM: bc writing to the DOM is expensive
• composable UI

Question 3

What is the Virtual DOM

Answer 3

an in memory representation of the real DOM and it syncs against the real DOM. The virtual DOM allows for cheaper and faster and more frequent updates

Question 4

When does the Virtual DOM sync against the real DOM?

Answer 4

After render() is called but before UI appears on screen

Question 5

How does the VirtualDOM work?

Answer 5

• when data changes, the entire UI in the vDOM updates
• then React calculates the diff between the vDOM and real DOM
• then the real DOM updates accordingly

Question 6

What is JSX?

Answer 6

It’s the UI language that allows us to write html with javascript

Question 7

Difference between state and props

Answer 7

• state is managed by the component
• props are passed into the component
• state re-renders the UI when updated
• props should be immutable and for configuration only

Question 8

When should you use a callback function in setState() ?

Answer 8

When you have to perform an asynchronous task

Question 9

What are the 3 phases of the component lifecycle?

Answer 9

• mount
• update
• unmount

Question 10

What are contexts?

Answer 10

tool to pass data w/o prop drilling. good for things like user auth or preferences

Question 11

What is a custom hook?

Answer 11

A function that allows us to “hook” into React’s state and lifecycle updates