4.7.md

Defining React Node Events

Events can be added to React nodes much like events can be added to DOM nodes. In the code example below I am adding a very simple click and mouseover event to a React <div> node.

source code

Note how the property name for an event in React starts with 'on' and is passed in the props argument object to the ReactElement() function.

React creates what it calls a SyntheticEvent for each event, which contains the details for the event. Similar to the details that are defined for DOM events. The SyntheticEvent instance, for an event, is passed into the events handlers/callback functions. In the code below I am logging the details of a SyntheticEvent instance.

source code

Every SyntheticEvent object instance has the following properties.

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

Additional properties are available depending upon the type/category of event that is used. For example the onClick syntheticEvent event also contains the following 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

The table below outlines the unique SyntheticEvent properties for each type/category of events.

Event Type/Category:	Events:	Event Specific Properties:
Clipboard	onCopy, onCut, onPaste	DOMDataTransfer, clipboardData
Composition	onCompositionEnd, onCompositionStart, onCompositionUpdate	data
Keyboard	onKeyDown, onKeyPress, onKeyUp	altKey, charCode, ctrlKey, getModifierState(key), key, keyCode, locale, location, metaKey, repeat, shiftKey, which
Focus	onChange, onInput, onSubmit	DOMEventTarget, relatedTarget
Form	onFocus, onBlur
Mouse	onClick, onContextMenu, onDoubleClick, onDrag, onDragEnd, onDragEnter, onDragExit onDragLeave, onDragOver, onDragStart, onDrop, onMouseDown, onMouseEnter, onMouseLeave onMouseMove, onMouseOut, onMouseOver, onMouseUp	altKey, button, buttons, clientX, clientY, ctrlKey, getModifierState(key), metaKey, pageX, pageY, DOMEventTarget relatedTarget, screenX, screenY, shiftKey,
Selection	onSelect
Touch	onTouchCancel, onTouchEnd, onTouchMove, onTouchStart	altKey DOMTouchList changedTouches, ctrlKey, getModifierState(key), metaKey, shiftKey, DOMTouchList targetTouches, DOMTouchList touches,
UI	onScroll	detail, DOMAbstractView view
Wheel	onWheel	deltaMode, deltaX, deltaY, deltaZ,
Media	onAbort, onCanPlay, onCanPlayThrough, onDurationChange, onEmptied, onEncrypted, onEnded, onError, onLoadedData, onLoadedMetadata, onLoadStart, onPause, onPlay, onPlaying, onProgress, onRateChange, onSeeked, onSeeking, onStalled, onSuspend, onTimeUpdate, onVolumeChange, onWaiting
Image	onLoad, onError
Animation	onAnimationStart, onAnimationEnd, onAnimationIteration	animationName, pseudoElement, elapsedTime
Transition	onTransitionEnd	propertyName, pseudoElement, elapsedTime

Notes

• React normalizes events so that they behave consistently across different browsers.
• Events in React are triggered on the bubbling phase. To trigger an event on the capturing phase add the word "Capture" to the event name (e.g., onClick would become onClickCapture).
• If you need the browser event details you can access this by using the nativeEvent property found in the SyntheticEvent object passed into React event hander/callback.
• React doesn't actually attach events to the nodes themselves, it uses event delegation.
• e.stopPropagation() or e.preventDefault() should be triggered manually to stop event propagation instead of return false;.
• Not all DOM events are provided by React. But you can still make use of them using React lifecycle methods.