useTransition react hook

The useTransition hook in React helps manage the prioritization of state updates. It allows you to mark certain updates as non-urgent, so they can be deferred to keep the UI responsive. This is particularly useful for heavy updates that might otherwise slow down the user interface.

How useTransition Works

1. Initial Setup: You call useTransition to get two values: isPending and startTransition.
2. Marking Updates: Use startTransition to wrap state updates that can be deferred.
3. Pending State: isPending is a boolean that indicates if a transition is ongoing.

Examples

Here are five examples to illustrate how useTransition can be used:

1. Filtering a List

   import { useState, useTransition } from 'react';

   function FilterList({ items }) {
     const [query, setQuery] = useState('');
     const [filteredItems, setFilteredItems] = useState(items);
     const [isPending, startTransition] = useTransition();

     const handleChange = (e) => {
       const value = e.target.value;
       setQuery(value);
       startTransition(() => {
         setFilteredItems(items.filter(item => item.includes(value)));
       });
     };

     return (
       <div>
         <input type="text" value={query} onChange={handleChange} />
         {isPending && <div>Loading...</div>}
         <ul>
           {filteredItems.map((item, index) => (
             <li key={index}>{item}</li>
           ))}
         </ul>
       </div>
     );
   }

2. Sorting a Table

   import { useState, useTransition } from 'react';

   function SortableTable({ data }) {
     const [sortKey, setSortKey] = useState('name');
     const [sortedData, setSortedData] = useState(data);
     const [isPending, startTransition] = useTransition();

     const handleSort = (key) => {
       setSortKey(key);
       startTransition(() => {
         setSortedData([...data].sort((a, b) => a[key].localeCompare(b[key])));
       });
     };

     return (
       <div>
         <button onClick={() => handleSort('name')}>Sort by Name</button>
         <button onClick={() => handleSort('age')}>Sort by Age</button>
         {isPending && <div>Sorting...</div>}
         <table>
           <thead>
             <tr>
               <th>Name</th>
               <th>Age</th>
             </tr>
           </thead>
           <tbody>
             {sortedData.map((item, index) => (
               <tr key={index}>
                 <td>{item.name}</td>
                 <td>{item.age}</td>
               </tr>
             ))}
           </tbody>
         </table>
       </div>
     );
   }

3. Loading More Items

   import { useState, useTransition } from 'react';

   function LoadMoreList({ initialItems }) {
     const [items, setItems] = useState(initialItems);
     const [isPending, startTransition] = useTransition();

     const loadMore = () => {
       startTransition(() => {
         fetch('/api/more-items')
           .then(response => response.json())
           .then(newItems => setItems([...items, ...newItems]));
       });
     };

     return (
       <div>
         <ul>
           {items.map((item, index) => (
             <li key={index}>{item}</li>
           ))}
         </ul>
         <button onClick={loadMore} disabled={isPending}>
           {isPending ? 'Loading...' : 'Load More'}
         </button>
       </div>
     );
   }

4. Updating a Chart

   import { useState, useTransition } from 'react';

   function Chart({ data }) {
     const [chartData, setChartData] = useState(data);
     const [isPending, startTransition] = useTransition();

     const updateChart = (newData) => {
       startTransition(() => {
         setChartData(newData);
       });
     };

     return (
       <div>
         <button onClick={() => updateChart(generateNewData())}>
           Update Chart
         </button>
         {isPending && <div>Updating...</div>}
         <ChartComponent data={chartData} />
       </div>
     );
   }

5. Navigating Between Tabs

   import { useState, useTransition } from 'react';

   function Tabs({ tabs }) {
     const [activeTab, setActiveTab] = useState(tabs[0]);
     const [isPending, startTransition] = useTransition();

     const handleTabClick = (tab) => {
       startTransition(() => {
         setActiveTab(tab);
       });
     };

     return (
       <div>
         <div className="tab-buttons">
           {tabs.map((tab, index) => (
             <button key={index} onClick={() => handleTabClick(tab)}>
               {tab}
             </button>
           ))}
         </div>
         {isPending && <div>Loading...</div>}
         <div className="tab-content">
           {activeTab}
         </div>
       </div>
     );
   }

Practice Exercises

Here are five practice exercises to help you get comfortable with useTransition:

1. Exercise 1: Create a search bar that filters a list of products. Use useTransition to defer the filtering operation.
2. Exercise 2: Implement a pagination system for a list of articles. Use useTransition to handle the loading of new pages.
3. Exercise 3: Build a dynamic form where adding new fields triggers a state update. Use useTransition to manage the addition of new fields.
4. Exercise 4: Develop a dashboard with multiple widgets. Use useTransition to update the data in the widgets without blocking the UI.
5. Exercise 5: Create a to-do list application where marking tasks as completed triggers a state update. Use useTransition to handle the update smoothly.

These exercises should help you get a good grasp of how to use the useTransition hook in various scenarios.