Function onFormSubmit

packages/next/src/client/form.tsx:90–169

(
  event: SubmitEvent<HTMLFormElement>,
  {
    actionHref,
    onSubmit,
    replace,
    scroll,
    router,
  }: {
    actionHref: string
    onSubmit: FormProps['onSubmit']
    replace: FormProps['replace']
    scroll: FormProps['scroll']
    router: NextRouter | null
  }
)

export default Form

function onFormSubmit(
  event: SubmitEvent<HTMLFormElement>,
  {
    actionHref,
    onSubmit,
    replace,
    scroll,
    router,
  }: {
    actionHref: string
    onSubmit: FormProps['onSubmit']
    replace: FormProps['replace']
    scroll: FormProps['scroll']
    router: NextRouter | null
  }
) {
  if (typeof onSubmit === 'function') {
    onSubmit(event)

    // if the user called event.preventDefault(), do nothing.
    // (this matches what Link does for `onClick`)
    if (event.defaultPrevented) {
      return
    }
  }

  if (!router) {
    // Form was somehow used outside of the router (but not in app/, the implementation is forked!).
    // We can't perform a soft navigation, so let the native submit handling do its thing.
    return
  }

  const formElement = event.currentTarget
  const submitter = event.nativeEvent.submitter

  let action = actionHref

  if (submitter) {
    // this is page-router-only, so we don't need to worry about false positives
    // from the attributes that react adds for server actions.
    if (hasUnsupportedSubmitterAttributes(submitter)) {
      return
    }

    // client actions have `formAction="javascript:..."`. We obviously can't prefetch/navigate to that.
    if (hasReactClientActionAttributes(submitter)) {
      return
    }

    // If the submitter specified an alternate formAction,
    // use that URL instead -- this is what a native form would do.
    // NOTE: `submitter.formAction` is unreliable, because it will give us `location.href` if it *wasn't* set
    // NOTE: this should not have `basePath` added, because we can't add it before hydration
    const submitterFormAction = submitter.getAttribute('formAction')
    if (submitterFormAction !== null) {
      if (process.env.NODE_ENV === 'development') {
        checkFormActionUrl(submitterFormAction, 'formAction')
      }