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

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support11 ?11 No11.6 No1
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes ?14 Yes No1 ?

1. Available on Nightly build (535.2)

See also


Document Tags and Contributors

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