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HTMLFormElement: formdata event

The formdata event fires after the entry list representing the form's data is constructed. This happens when the form is submitted, but can also be triggered by the invocation of a FormData() constructor.

This event is not cancelable and does not bubble.

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

js

addEventListener("formdata", (event) => {});

onformdata = (event) => {};

Event type

Event properties

Inherits properties from its parent interface, Event.

FormDataEvent.formData

Contains the FormData object representing the data contained in the form when the event was fired.

Examples

js

// grab reference to form

const formElem = document.querySelector("form");

// submit handler

formElem.addEventListener("submit", (e) => {
  // on form submission, prevent default
  e.preventDefault();

  console.log(formElem.querySelector('input[name="field1"]')); // FOO
  console.log(formElem.querySelector('input[name="field2"]')); // BAR

  // construct a FormData object, which fires the formdata event
  const formData = new FormData(formElem);
  // formdata gets modified by the formdata event
  console.log(formData.get("field1")); // foo
  console.log(formData.get("field2")); // bar
});

// formdata handler to retrieve data

formElem.addEventListener("formdata", (e) => {
  console.log("formdata fired");

  // modifies the form data
  const formData = e.formData;
  // formdata gets modified by the formdata event
  formData.set("field1", formData.get("field1").toLowerCase());
  formData.set("field2", formData.get("field2").toLowerCase());
});

The onformdata version would look like this:

js

formElem.onformdata = (e) => {
  console.log("formdata fired");

  // modifies the form data
  const formData = e.formData;
  formData.set("field1", formData.get("field1").toLowerCase());
  formData.set("field2", formData.get("field2").toLowerCase());
};

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
formdata_event 77 79 72 No 64 15 77 77 79 55 15 12.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/HTMLFormElement/formdata_event