SyntheticEvent

This reference guide documents the SyntheticEvent wrapper that forms part of React’s Event System. See the Handling Events guide to learn more.

Overview

Your event handlers will be passed instances of SyntheticEvent, a cross-browser wrapper around the browser’s native event. It has the same interface as the browser’s native event, including stopPropagation() and preventDefault(), except the events work identically across all browsers.

If you find that you need the underlying browser event for some reason, simply use the nativeEvent attribute to get it. Every SyntheticEvent object has the following attributes:

boolean bubbles boolean cancelable DOMEventTarget currentTarget boolean defaultPrevented number eventPhase boolean isTrusted DOMEvent nativeEvent void preventDefault() boolean isDefaultPrevented() void stopPropagation() boolean isPropagationStopped() DOMEventTarget target number timeStamp string type

Note:

As of v0.14, returning false from an event handler will no longer stop event propagation. Instead, e.stopPropagation() or e.preventDefault() should be triggered manually, as appropriate.

Event Pooling

The SyntheticEvent is pooled. This means that the SyntheticEvent object will be reused and all properties will be nullified after the event callback has been invoked. This is for performance reasons. As such, you cannot access the event in an asynchronous way.

function onClick(event) { console.log(event); // => nullified object. console.log(event.type); // => "click" const eventType = event.type; // => "click" setTimeout(function() { console.log(event.type); // => null console.log(eventType); // => "click" }, 0); // Won't work. this.state.clickEvent will only contain null values. this.setState({clickEvent: event}); // You can still export event properties. this.setState({eventType: event.type}); }

Note:

If you want to access the event properties in an asynchronous way, you should call event.persist() on the event, which will remove the synthetic event from the pool and allow references to the event to be retained by user code.

Supported Events

React normalizes events so that they have consistent properties across different browsers.

The event handlers below are triggered by an event in the bubbling phase. To register an event handler for the capture phase, append Capture to the event name; for example, instead of using onClick, you would use onClickCapture to handle the click event in the capture phase.


Reference

Clipboard Events

Event names:

onCopy onCut onPaste

Properties:

DOMDataTransfer clipboardData


Composition Events

Event names:

onCompositionEnd onCompositionStart onCompositionUpdate

Properties:

string data


Keyboard Events

Event names:

onKeyDown onKeyPress onKeyUp

Properties:

boolean altKey number charCode boolean ctrlKey boolean getModifierState(key) string key number keyCode string locale number location boolean metaKey boolean repeat boolean shiftKey number which

The key property can take any of the values documented in the DOM Level 3 Events spec.


Focus Events

Event names:

onFocus onBlur

These focus events work on all elements in the React DOM, not just form elements.

Properties:

DOMEventTarget relatedTarget


Form Events

Event names:

onChange onInput onInvalid onSubmit

For more information about the onChange event, see Forms.


Mouse Events

Event names:

onClick onContextMenu onDoubleClick onDrag onDragEnd onDragEnter onDragExit onDragLeave onDragOver onDragStart onDrop onMouseDown onMouseEnter onMouseLeave onMouseMove onMouseOut onMouseOver onMouseUp

The onMouseEnter and onMouseLeave events propagate from the element being left to the one being entered instead of ordinary bubbling and do not have a capture phase.

Properties:

boolean altKey number button number buttons number clientX number clientY boolean ctrlKey boolean getModifierState(key) boolean metaKey number pageX number pageY DOMEventTarget relatedTarget number screenX number screenY boolean shiftKey


Pointer Events

Event names:

onPointerDown onPointerMove onPointerUp onPointerCancel onGotPointerCapture onLostPointerCapture onPointerEnter onPointerLeave onPointerOver onPointerOut

The onPointerEnter and onPointerLeave events propagate from the element being left to the one being entered instead of ordinary bubbling and do not have a capture phase.

Properties:

As defined in the W3 spec, pointer events extend Mouse Events with the following properties:

number pointerId number width number height number pressure number tangentialPressure number tiltX number tiltY number twist string pointerType boolean isPrimary

A note on cross-browser support:

Pointer events are not yet supported in every browser (at the time of writing this article, supported browsers include: Chrome, Firefox, Edge, and Internet Explorer). React deliberately does not polyfill support for other browsers because a standard-conform polyfill would significantly increase the bundle size of react-dom.

If your application requires pointer events, we recommend adding a third party pointer event polyfill.


Selection Events

Event names:

onSelect


Touch Events

Event names:

onTouchCancel onTouchEnd onTouchMove onTouchStart

Properties:

boolean altKey DOMTouchList changedTouches boolean ctrlKey boolean getModifierState(key) boolean metaKey boolean shiftKey DOMTouchList targetTouches DOMTouchList touches


UI Events

Event names:

onScroll

Properties:

number detail DOMAbstractView view


Wheel Events

Event names:

onWheel

Properties:

number deltaMode number deltaX number deltaY number deltaZ


Media Events

Event names:

onAbort onCanPlay onCanPlayThrough onDurationChange onEmptied onEncrypted onEnded onError onLoadedData onLoadedMetadata onLoadStart onPause onPlay onPlaying onProgress onRateChange onSeeked onSeeking onStalled onSuspend onTimeUpdate onVolumeChange onWaiting


Image Events

Event names:

onLoad onError


Animation Events

Event names:

onAnimationStart onAnimationEnd onAnimationIteration

Properties:

string animationName string pseudoElement float elapsedTime


Transition Events

Event names:

onTransitionEnd

Properties:

string propertyName string pseudoElement float elapsedTime


Other Events

Event names:

onToggle

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