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The detail readonly property of the CustomEvent interface returns any data passed when initializing the event.

Note: This feature is available in Web Workers.


 let myDetail = customEventInstance.detail;

Return value

Whatever data the event was initialized with.


// add an appropriate event listener
obj.addEventListener("cat", function(e) { process(e.detail) });

// create and dispatch the event
let event = new CustomEvent("cat", {
  detail: {
    hazcheeseburger: true

// Will return an object contaning the hazcheeseburger property
let myDetail = event.detail;


Specification Status Comment
The definition of 'detail' in that specification.
Living Standard Initial definition.

Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
BasicSupport 15 11 (11) No support 11.60 Nightly build (535.2)
Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support ? 11.0 (11) ? ? ?

See also


Document Tags and Contributors

 Contributors to this page: chrisdavidmills
 Last updated by: chrisdavidmills,