function submitPopup(overlay) {
	const form = document.querySelector('#massupdate-form');
	const action = form.querySelector('#action').value;
	const location_url = form.querySelector('#location_url').value;
	let macros_removeall_warning = (form.querySelector('#visible_macros:checked')
		&& form.querySelector('[name="mass_update_macros"][value="3"]:checked')
		&& (form.querySelector('#macros_remove_all').checked === false)
	);
	let valuemaps_removeall_warning = (form.querySelector('#visible_valuemaps:checked')
		&& form.querySelector('[name="valuemap_massupdate"][value="3"]:checked')
		&& (form.querySelector('#valuemap_remove_all').checked === false)
	);
	let warning_message = '';

	if (macros_removeall_warning) {
		warning_message = "Please confirm that you want to remove all macros.";
	}
	else if (valuemaps_removeall_warning) {
		warning_message = "Please confirm that you want to remove all value mappings.";
	}

	if (warning_message !== '') {
		overlayDialogue({
			'title': "Warning",
			'type': 'popup',
			'class': 'position-middle',
			'content': $('<span>').text(warning_message),
			'buttons': [
				{
					'title': "Ok",
					'focused': true,
					'action': () => {}
				}
			]
		}, overlay.$btn_submit);

		overlay.unsetLoading();
		return false;
	}

	if (form.querySelector('#visible_valuemaps:checked')) {
		$(form).trimValues(['[name^="valuemap_rename["]']);
	}

	if (form.querySelector('#visible_tags:checked')) {
		$(form).trimValues(['[name^="tags"][name$="[tag]"]', '[name^="tags"][name$="[value]"]']);
	}

	if (action == 'popup.massupdate.host') {
		// Depending on checkboxes, create a value for hidden field 'tls_accept'.
		let tls_accept = 0x00;

		if (form.querySelector('#tls_in_none') && form.querySelector('#tls_in_none').checked) {
			tls_accept |= 1;
		}
		if (form.querySelector('#tls_in_psk') && form.querySelector('#tls_in_psk').checked) {
			tls_accept |= 2;
		}
		if (form.querySelector('#tls_in_cert') && form.querySelector('#tls_in_cert').checked) {
			tls_accept |= 4;
		}

		form.querySelector('#tls_accept').value = tls_accept;
	}

	// Remove error message.
	overlay.$dialogue.find('.msg-bad').remove();

	const url = new Curl('zabbix.php');
	url.setArgument('action', action);
	url.setArgument('output', 'ajax');

	fetch(url.getUrl(), {
		method: 'post',
		headers: {'Content-Type': 'application/x-www-form-urlencoded;charset=UTF-8'},
		body: $(form).serialize()
	})
	.then((response) => response.json())
	.then((response) => {
		if ('script_inline' in response) {
			$('head').append(response.script_inline);
		}

		if ('error' in response) {
			overlay.unsetLoading();

			const message_box = makeMessageBox('bad', response.error.messages, response.error.title);

			message_box.insertBefore(form);
		}
		else if (action === 'item.prototype.massupdate' || action === 'item.massupdate') {
			// Item and item prototype lists javascript handles successful update.
			overlayDialogueDestroy(overlay.dialogueid);
			overlay.$dialogue[0].dispatchEvent(new CustomEvent('dialogue.submit', {detail: response}));
		}
		else {
			postMessageOk(response.title);

			if ('messages' in response) {
				postMessageDetails('success', response.messages);
			}

			overlayDialogueDestroy(overlay.dialogueid);
			location.href = location_url;
		}
	});
}