LuCI, cgi-download question

[iuncuim]

I am trying to make a web page where I can download some files using a cgi-download. I found an example in the flash.js.
What I want - to run a fs.exec that will generate a file that can be obtained in the browser. How can i do this?
This is my attempt:

	handleReport: function(ev) {
		fs.exec('/bin/report',null);
		var form = E('form', {
			'method': 'post',
			'action': L.env.cgi_base + '/cgi-download',
			'enctype': 'application/x-www-form-urlencoded'
		}, [
			E('input', { 'type': 'hidden', 'name': 'sessionid', 'value': rpc.getSessionID() }),
			E('input', { 'type': 'hidden', 'name': 'path',      'value': '/tmp/report.tar.gz' }),
			E('input', { 'type': 'hidden', 'name': 'filename',  'value': 'report.tar.gz' })
		]);
		ev.currentTarget.parentNode.appendChild(form);
		form.submit();
		form.parentNode.removeChild(form);
	},
	render: function() {
			...
		o = s.option(form.Button, 'dl_report',_(' '));
		o.inputstyle = 'action important';
		o.inputtitle = _('Generate archive');
		o.onclick = this.handleReport;

		return m.render();
	},

On the first click, I get error:
"Failed to stat requested path: No such file or directory"
The second click on the button is successful, I can upload the file.
I think that the problem is that the file does not have time to be formed the first time.

P.S.: Sorry for my english and js

[iuncuim]

This solution works:

		o = s.option(form.Button, 'dl_report',_(' '));
		o.inputstyle = 'action important';
		o.inputtitle = _('Generate archive');
		o.onclick = function(ev) {
			this.map.save();
			fs.exec('/bin/report',null).then(function(res) {
				var form = E('form', {
					'method': 'post',
					'action': L.env.cgi_base + '/cgi-download',
					'enctype': 'application/x-www-form-urlencoded'
				}, [
					E('input', { 'type': 'hidden', 'name': 'sessionid', 'value': rpc.getSessionID() }),
					E('input', { 'type': 'hidden', 'name': 'path',      'value': '/tmp/report.tar.gz' }),
					E('input', { 'type': 'hidden', 'name': 'filename',  'value': 'report.tar.gz' })
				]);
				ev.target.parentNode.appendChild(form);
				form.submit();
				form.parentNode.removeChild(form);
			},this,ev.target);
		}

[iuncuim]

Can someone explain how to apply unsaved changes properly on luci(js) page?