With a Handlebars.js template like this...
If you have very few options and you don't want to write a helper, here is what you can do:
//app.js
var data = {selectedVal: 'b'};
// can also use switch ... case ...
if (data.selectedVal === 'a') {
data.optionASelected = true;
} else if (data.selectedVal === 'b') {
data.optionBSelected = true;
}
// assuming you have a template function to handle this data
templateFunc(data);
In your template file:
Again this may NOT be the best solution of all, but it probably is a very quick work around when you are dealing very few options and wanted a quick fix.