This cheatsheet contains live examples of a number of common React events. You can learn more about events in the Everything About Events chapter of Learn React By Itself.
There are still a number of events with no examples, but I will be adding more! For a full reference without examples, you can see React’s official documentation. If there are any events in particular that you’d like to see examples for, drop me a line at james@sevenstripes.com.
Keyboard events can be used with any focusable element. This includes HTML form elements, as well as any element with a tabIndex
property.
• onKeyDown
is called when a key is depressed
• onKeyPress
is called after the key is released, but before onKeyUp
is triggered
• onKeyUp
is called last, after the key is pressed
To check the key that was pressed, use the key
property. This holds a string that represents the key.
The altKey
, ctrlKey
, metaKey
and shiftKey
properties let you check if a modifier key was depressed at the time of the event. These are all booleans.
A numeric keyCode
property is also available, but try to avoid this as it will make your code harder to read.
• onBlur
is called when a control loses focus
• onFocus
is called when a control receives focus
When switching between elements, onBlur
will always be called before onFocus
.
It is probably best to avoid the event object for focus events, as browser support for the underlying events varies significantly. In particular, the preventDefault()
method will not work reliably.
See how focus and blur events are fired by clicking on a button, and using the Tab or shift-Tab key combinations to navigate between them.
• onChange
is called when the user changes the value in a form control.
• onInput
is identical to onChange
. Prefer onChange
where possible.
• onSubmit
is a special prop for <form>
elements that is called when a <button type='submit'>
is pressed, or when the user hits the return key within a field.
For onChange
, the event.target
object allows you to acces the control’s DOM node. You can then use event.target.value
to get the new value that was entered into the control.
The event.preventDefault()
method allows you to prevent default behavior. When used within onSubmit
, this will prevent the browser from navigating to a new page. When used within onChange
, it will prevent whatever character was entered from being added to the control.
• onClick
: a mouse button was pressed and released. Called before onMouseUp
.
• onContextMenu
: the right mouse button was pressed.
• onDoubleClick
• onMouseDown
: a mouse button is depressed
• onMouseEnter
: the mouse moves over an element or its children
• onMouseLeave
: the mouse leaves an element
• onMouseMove
• onMouseOut
: the mouse moves off of an element, or onto one of its children
• onMouseOver
: the mouse moves directly over an element
• onMouseUp
: a mouse button was released
React’s drag and drop events have access to the same event object properties as the mouse events. However, I’d recommend using react-dnd instead of using the raw events where possible. For reference, the drag/drop events are:
onDrag
onDragEnd
onDragEnter
onDragExit
onDragLeave
onDragOver
onDragStart
onDrop
The button
property holds a number that represents which mouse button was pressed. This will be 0
for the left button and 1
for the middle button. Theoretically, 2
represents the right button, but most browsers will not trigger any events other than onContextMenu
when the right button is pressed.
The properties altKey
, ctrlKey
, metaKey
and shiftKey
allow you to check if a modifier key was pressed on your keyboard when the event was triggered, just like with keyboard events. These are all booleans.
The preventDefault()
method can be used to cancel default click actions. For example, to prevent the browser from navigating when a link is clicked, you can call event.preventDefault()
within an <a>
element’s onClick
handler.
There are also a number of positioning properties:
• clientX
and clientY
contain the coordinates measured from the top left of the visible part of the page (regardless of the scroll position)
• pageX
and pageY
contain the coordinates from the top of the page – which may be currently off-screen due to scrolling.
• screenX
and screenY
give the position within the entire screen.
Hover your mouse over the preview area to see the values of the positioning properties.
Without event.preventDefault()
, clicking the link in the preview pane would reload the page.
Try left and right clicking the different buttons to see whether the events work.
Note how onMouseEnter
and onMouseLeave
are only called when you move your mosue over the red box, while onMouseOver
and onMouseOut
are called when the mouse movers over the blue child too.
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