Вариант с селектором (селектор можно генерить и динамически - по массиву fams)
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>font-family</title>
</style>
</head>
<body>
<h1>Duis te feugifacilisi</h1>
<p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diem
nonummy nibh euismod tincidunt ut lacreet dolore magna aliguam erat volutpat.
Ut wisis enim ad minim veniam, quis nostrud exerci tution ullamcorper suscipit
lobortis nisl ut aliquip ex ea commodo consequat.</p>
<select id='selfont'>
<option disabled>Выберите шрифт</option>
<option selected value='Tangerine'>Tangerine</option>
<option value='Inconsolata'>Inconsolata</option>
<option value='Eater'>Eater</option>
</select>
<script src="https://ajax.googleapis.com/ajax/libs/webfont/1/webfont.js" type="text/javascript" async=""></script>
<script>
var body = document.querySelector('body')
fams = [ 'Tangerine','Inconsolata','Eater' ];
WebFontConfig = {
google: { families: fams },
fontactive: function() {
body.style.fontFamily = 'Tangerine';
}
};
selfont.onchange = function() {
body.style.fontFamily = this.value;
}
</script>
</body>
</html>