React でのイベント処理

Event handling in React allows you to respond to user interactions like clicks, form submissions, and other events. Here’s a basic overview and example:

Basic Concepts

1. Event Binding: In React, you typically use camelCase for event names (e.g., onClick, onChange).
2. Event Handling: You can pass a function as an event handler directly in JSX.
3. Synthetic Events: React wraps the native events in a synthetic event to ensure cross-browser compatibility.

Example

Here's a simple example of handling a button click and an input change:

import React, { useState } from 'react';

const EventHandlingExample = () => {
  const [inputValue, setInputValue] = useState('');

  const handleClick = () => {
    alert(`Button clicked! Input value: ${inputValue}`);
  };

  const handleChange = (event) => {
    setInputValue(event.target.value);
  };

  return (
    <div>
      <input 
        type="text" 
        value={inputValue} 
        onChange={handleChange} 
        placeholder="Type something..." 
      />
      <button onClick={handleClick}>Click Me</button>
    </div>
  );
};

export default EventHandlingExample;

Key Points

• State Management: Use useState to manage the state in functional components.
• Event Object: The event handler receives an event object that contains information about the event.
• Prevent Default: Use event.preventDefault() to prevent the default behavior of events (like form submissions).

Feel free to ask if you need specific examples or further explanations!

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