SO Answer

See: http://stackoverflow.com/questions/6775192/how-to-use-html5-file-api-with-unobtrusive-javascript/6775225#6775225

by KooiInc MeHere

HTML

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"/>
<script>
window.onload = function() {
    var input2 = document.getElementById('input2');
    input2.addEventListener('change', handleFiles, false);
}

function handleFiles(e) {
    alert('got files');
}
</script>
</head>
<body>
<h1>Test</h1>
<input type="file" id="input1"/>
<input type="file" id="input2"/>
</body>
</html>