The second of those is exactly the approach I've taken in the couple client-side web apps that I've built. I initially generate and insert generic DOM fragments

The second of those is exactly the approach I've taken in the couple client-side web apps that I've built. I initially generate and insert generic DOM fragments from templates, but only use the template to fill in values that I know will not change throughout the lifetime of the view (the "templates" often don't have parameters). After that, I use one code path both for the initial value setting and for subsequent updates. If I'm not mistaken, this is more or less the approach used in Knockout and AngularJS.