type
{string}listener
{Function|EventListener}options
{Object}once
{boolean} Whentrue
, the listener is automatically removed when it is first invoked. Default:false
.passive
{boolean} Whentrue
, serves as a hint that the listener will not call theEvent
object’spreventDefault()
method. Default:false
.capture
{boolean} Not directly used by Node.js. Added for API completeness. Default:false
.
Adds a new handler for the type
event. Any given listener
is added
only once per type
and per capture
option value.
If the once
option is true
, the listener
is removed after the
next time a type
event is dispatched.
The capture
option is not used by Node.js in any functional way other than
tracking registered event listeners per the EventTarget
specification.
Specifically, the capture
option is used as part of the key when registering
a listener
. Any individual listener
may be added once with
capture = false
, and once with capture = true
.
function handler(event) {}
const target = getEventTargetSomehow();
target.addEventListener('foo', handler, { capture: true }); // first
target.addEventListener('foo', handler, { capture: false }); // second
// Removes the second instance of handler
target.removeEventListener('foo', handler);
// Removes the first instance of handler
target.removeEventListener('foo', handler, { capture: true });