Class 03 Reading Notes

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Table of Contents

1. React Lists and Keys
2. The Spread Operator
3. Passing Functions Between Components

React Lists and Keys

• What does .map() return? **
• If I want to loop through an array and display each value in JSX, how do I do that in React? embedding the JS map() function into the HTML element using curly braces
• Each list item needs a unique __. Key
• What is the purpose of a key? To give the elements a stable identity. Typically use and ID

The Spread Operator

• What is the spread operator? Expands an iterable object array into lists of arguments
• List 4 things that the spread operator can do. Copy an array, concatenate or combine arrays, match functions, adding item to a list
• Give an example of using the spread operator to combine two arrays. […arr1,…arr2] returns all of the elements of both arrays
• Give an example of using the spread operator to add a new item to an array. If you have an existng array arr1, you can dclare a new variable and assign [item1, item2, …arr1] and it will combine those new items into the new declared array

Passing Functions Between Components

• In the video, what is the first step that the developer does to pass functions between components?
• In your own words, what does the increment function do?
• How can you pass a method from a parent component into a child component?
• How does the child component invoke a method that was passed to it from a parent component?