What is Synthetic Event?

A Synthetic Event in React is a wrapper around the native DOM event that provides a consistent and cross-browser interface for handling events in React applications.

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Why Synthetic Events?

• Different browsers handle events differently, which can cause inconsistencies.
• React’s SyntheticEvent normalizes event behavior across browsers, ensuring that event properties work the same everywhere.

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Key Points About Synthetic Events:

Feature	Description
Cross-Browser Compatibility	Handles browser inconsistencies automatically.
Pooling	Reuses event objects for performance optimization.
Event Properties	Access event properties like target, type, currentTarget.
Stop Propagation & Prevent Default	Supports e.stopPropagation() and e.preventDefault() like native events.

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Example:

javascriptCopyEditfunction ButtonClick() {
  const handleClick = (e) => {
    console.log(e.type); // Synthetic Event
    console.log(e.target); // Element that triggered the event
    e.preventDefault();
  };

  return <button onClick={handleClick}>Click Me</button>;
}

• e is a SyntheticEvent object.
• Properties like e.type, e.target, e.preventDefault() work similarly to native events.

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Synthetic Event Pooling:

React pools SyntheticEvent objects to improve performance.

• Events are re-used after the event callback is executed.
• Accessing event properties asynchronously can lead to issues.

Example:

javascriptCopyEditfunction App() {
  const handleClick = (e) => {
    console.log(e.type); // Works fine
    setTimeout(() => {
      console.log(e.type); // May not work due to pooling
    }, 1000);
  };

  return <button onClick={handleClick}>Click Me</button>;
}

Solution – Use e.persist():

javascriptCopyEditconst handleClick = (e) => {
  e.persist(); // Prevents the event from being reused
  setTimeout(() => {
    console.log(e.type); // Now works as expected
  }, 1000);
};

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Benefits of Synthetic Events:

Abstracts browser differences – consistent behavior across browsers.
Performance optimized – Event pooling reduces memory usage.
Consistent API – Unified event properties like target, type.

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Summary:

Synthetic Event is React’s abstraction over native DOM events.
It normalizes event handling across browsers and improves performance through event pooling.
Use e.persist() if accessing event data asynchronously.