Lists and Keys

• What does .map() return? return a new array after modification, But without affect the original array with these modifications.

• If I want to loop through an array and display each value in JSX, how do I do that in React? make an arrow/map function and return a html value in each time, after that we render it to the DOM. see the example :

ReactDOM.render(

{listItems}

, document.getElementById(‘root’) );

• Each list item needs a unique __. key
• What is the purpose of a key? keys help React identify which items have changed, are added, or are removed. Keys should be given to the elements inside the array to give the elements a stable identity.