reading-notes

list and keys

1. What does .map() return?
   • Map returns the new array
2. If I want to loop through an array and display each value in JSX, how do I do that in React?
   • You would use a {}
3. Each list item needs a unique __.
   • key
4. What is the purpose of a key?

• to indentify what has moved or been modified

The Spread Operator

1. What is the spread operator?

• it is three dots to expand itarable objects in the list of arguments

1. List 4 things that the spread operator can do.

• spreads the array into seperate arguments

• concatenating or combining arrays

• Adding an item to a list

• Adding to state in React

1. Give an example of using the spread operator to combine two arrays.
   • ‘[…[“😋😛😜🤪😝”]] // Array [ “😋😛😜🤪😝” ] […“🙂🙃😉😊😇🥰😍🤩!”] // Array(9) [ “🙂”, “🙃”, “😉”, “😊”, “😇”, “🥰”, “😍”, “🤩”, “!” ]`

const hello = {hello: "😋😛😜🤪😝"} const world = {world: "🙂🙃😉😊😇🥰😍🤩!"}

const helloWorld = {...hello,...world} console.log(helloWorld) // Object { hello: "😋😛😜🤪😝", world: "🙂🙃😉😊😇🥰😍🤩!" }

1. Give an example of using the spread operator to add a new item to an array.

• see above

1. Give an example of using the spread operator to combine two objects into one.

• see above

How to Pass Functions Between Components

1. In the video, what is the first step that the developer does to pass functions between components?

• create the function wherever the state is

1. In your own words, what does the increment function do?
   • modifying an array
   • finding the name
   • its going to loop through the array
   • update our stat object
2. How can you pass a method from a parent component into a child component?

• `{this.props}’

1. How does the child component invoke a method that was passed to it from a parent component?
   • you toggle it