Which is better/more maintainable, using Javascript to initialize the values of the different HTML controls or writing inline <% %> tags?
The current page I am writing has many HTML controls and I'm afreaid that putting inline ASP would make it too unmaintainable.
Well... using JS to populate the controls with values will make the whole solution useless in JS-free environments. This is not what the webdev community calls unobtrussive.
As you don´t define better any better (!) I would say go for the inline rendering.
If you really have millions (I really doubt this number) of HTML Controls in your page I would say you need to get back to the drawing board and re-architect the solution.
If you've really got loads and loads of HTML controls in an ASP.Net page, you might have to rethink your design. Why aren't you using server controls?
However, you can always use the runtat="server" attribute on HTML elements to effectively turn them into server-side controls. You can then work with them in much the same way as ASP.Net controls. You may want to watch out for extra Viewstate being added, though.
You are going to have the same problem regardless of the method: maintainability.
I have some legacy forms that need to remember some fields between calls, so I have a lot of code that might be a little ugly, but if you stick to a standard, doesn't get too messy.
<label for="email<%=i%>">E-Mail<% if required then %> (*)<% end if %>:</label>
<input name="email<%=i%>" id="email<%=i%>" type="text" value="<%=Trim(request.form("email"&i))%>" />
The problem is that it involves a lot of copy paste when having to add a new control. You could make a function to build it and keep the code duplication to a minimum.
<%= BuildHTMLInputControl("email"&i, "text", "E-Mail", true) %>
' Response: <label for="email1">E-Mail (*):</label><input name="email1" id="email1" type="text" value="Previous Value" />
I haven't done something like this, because it hasn't been a concern yet in the small forms that I've done this.
The advantage of this is that the fields are populated onload, there is no flashing of content and you are really friendly to non-Javascript users, something that you should be.
The only difference would be that with javascript youd have a lot of document.getElementById() at the beggining (or rather end) of the document, that increases the HTML file size (which might be a concern) and could not populate the fields instantly.
What is better/more maintainable, using Javascript to initialize the values of the different HTML controls or writing inline <% %> tags?
I wouldn't do it either way. That sounds like old-style ASP, or maybe PHP or JSP-type logic.
The ASP.NET model is to use controls on the page, and then to set the values of those controls either from code-behind or in-line code, possibly using some type of data binding. Separating the display logic from the data is much, much easier to maintain.