Passing Functions as Props

Lists and Keys

1. What does .map() return?
   • .map() returns a new array
2. If I want to loop through an array and display each value in JSX, how do I do that in React?
   • wrap the js code with {} and then use .map(num => <>{num}</>) to render it
3. Each list item needs a unique __.
   • key
4. What is the purpose of a key?
   • Keys help React identify which items have changed, are added, or are removed.

The Spread Operator

1. What is the spread operator?
   • a useful and quick syntax for adding items to arrays, combining arrays or objects, and spreading an array out into a function’s arguments
2. List 4 things that the spread operator can do.
   • Copying an array
   • Concatenating or combining arrays
   • Using Math functions
   • Using an array as arguments
3. Give an example of using the spread operator to combine two arrays.
   • const arr3 = {...arr1,...arr2}
4. Give an example of using the spread operator to add a new item to an array.
   • arr1 = [...arr1, newNumber]
5. Give an example of using the spread operator to combine two objects into one.
   • const objectThree = {...objectOne, ...objectTwo}

More on lists and keys

More on the spread operator

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