However, that introduces the potential for event listeners handling touch events and wheel events to block the browser's main thread while the browser is attempting to handle scrolling - possibly resulting in an enormous reduction in performance during scroll handling. The specification for addEventListener() defines the default value for the passive option as always being false. Let passiveSupported = false try, passiveIfSupported ) If not specified, useCapture defaults to false. See DOM Level 3 Events and JavaScript Event order for a detailed explanation. The event propagation mode determines the order in which elements receive That is nested within another element, when both elements have registered a handle for Eventīubbling and capturing are two ways of propagating events that occur in an element Upward through the tree will not trigger a listener designated to use capture. The registered listener before being dispatched toĪny EventTarget beneath it in the DOM tree. useCapture OptionalĪ boolean value indicating whether events of this type will be dispatched to If not specified, no AbortSignal is associated with the listener. The listener will be removed when the given AbortSignal object's abort() method is called. See Improving scrolling performance with passive listeners to learn more.Īn AbortSignal. If not specified, defaults to false – except that in browsers other than Safari and Internet Explorer, defaults to true for the wheel, mousewheel, touchstart and touchmove events. If not specified, defaults to false.Ī boolean value that, if true, indicates that the functionĭoes call preventDefault(), the user agent will do nothing other than Listener would be automatically removed when invoked. Should be invoked at most once after being added. If not specified, defaults to false.Ī boolean value indicating that the listener

To the registered listener before being dispatched to anyĮventTarget beneath it in the DOM tree. The availableĪ boolean value indicating that events of this type will be dispatched The event listener callback for details on the callback itself.Īn object that specifies characteristics about the event listener. This mustīe null, an object with a handleEvent() method, or a JavaScript The object that receives a notification (an object that implements theĮvent interface) when an event of the specified type occurs. A case-sensitive string representing the event type to listen for.

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