Ajit_Kumar_Frontend

[AjitJeet]

1. A React component that shows a list of things is called the basic List component. Each item is rendered as a SingleListItem component when the function gets an array of items as a parameter and maps over the array. Depending on whether it is selected or not, the background colour of the text displayed by each SingleListItem component, which represents a single item in the list, varies. The selected index of the list item is tracked by the List component using the useState and useEffect hooks, and it is reset when the items prop changes. A handleClick method is called when a SingleListItem is clicked, setting the selected index to the clicked item's index.

2. (a) In the WrappedListComponent, the useState hook is not used correctly. The setSelectedIndex function should be declared as const [selectedIndex, setSelectedIndex] = useState(null);, with selectedIndex being the current state value and setSelectedIndex being the function that can be used to update the state.

(b) The PropTypes.array method is not used correctly. Instead of calling PropTypes.array and passing the PropTypes.shapeOf object as an argument, it should be called as PropTypes.arrayOf and passed the individual PropTypes as an argument. So, it should be PropTypes.arrayOf(PropTypes.shape({...})).

(c) In the SingleListItem component, the onClickHandler function is being called immediately instead of being passed as a callback function. This will cause the function to be executed on every render of the component, which is not what is intended. Instead, it should be wrapped in an arrow function or passed as a reference like this: onClick={() => onClickHandler(index)}.

(d) In the SingleListItem component, the isSelected prop is expected to be a boolean but is being set to the selectedIndex state value, which is a number. This could cause issues with the background color rendering, and the isSelected prop should instead be set to a boolean value that indicates whether the current index is selected or not.

(e) WrappedSingleListItem and WrappedListComponent may not be necessary since they are relatively simple components without complex logic or expensive rendering operations. This could add unnecessary complexity to the code and slow down performance.

3. 
   import React, { useState, useEffect, memo } from 'react';
   import PropTypes from 'prop-types';

// Single List Item const WrappedSingleListItem = ({ index, isSelected, onClickHandler, text, }) => { return ( <li style={{ backgroundColor: isSelected ? 'green' : 'red'}} onClick={() => onClickHandler(index)}

{text} ); };

WrappedSingleListItem.propTypes = { index: PropTypes.number, isSelected: PropTypes.bool, onClickHandler: PropTypes.func.isRequired, text: PropTypes.string.isRequired, };

const SingleListItem = memo(WrappedSingleListItem);

// List Component const WrappedListComponent = ({ items, }) => { const [selectedIndex, setSelectedIndex] = useState(null);

useEffect(() => { setSelectedIndex(null); }, [items]);

const handleClick = index => { setSelectedIndex(index); };

return ( <ul style={{ textAlign: 'left' }}> {items.map((item, index) => ( <SingleListItem key={index} onClickHandler={() => handleClick(index)} text={item.text} index={index} isSelected={selectedIndex === index} /> ))} ) };

WrappedListComponent.propTypes = { items: PropTypes.arrayOf(PropTypes.shape({ text: PropTypes.string.isRequired })).isRequired, };

WrappedListComponent.defaultProps = { items: [], };

const List = memo(WrappedListComponent);

export default List;