Class Roo.MasterTemplate

var t = new Roo.MasterTemplate(
	'<select name="{name}">',
		'<tpl name="options"><option value="{value:trim}">{text:ellipsis(10)}</option></tpl>',
	'</select>'
);
t.add('options', {value: 'foo', text: 'bar'});
// or you can add multiple child elements in one shot
t.addAll('options', [
    {value: 'foo', text: 'bar'},
    {value: 'foo2', text: 'bar2'},
    {value: 'foo3', text: 'bar3'}
]);
// then append, applying the master template values
t.append('my-form', {name: 'my-select'});