Question

I have some functionality on my page that JavaScript is currently handling. I want to make my page compatible with non-Javascript users. Is there a way I can say “If JavaScript is enabled, use my JavaScript routine, otherwise do a Postback and let the server-side handle it?”

Answer 1

I have to presume that whatever triggers this postback or client-side behaviour (depending on javascript being available or not) is a html submit button?

If it is, I would attach the javascript handler for the client-side stuff to the button and have the handler return ‘false’ to prevent postback. When javascript is not enabled, the button will perform the standard html form function of triggering a postback and that will then let you do things server-side instead.

You can do a similar thing for links by having javascript run on the link click event to do client-side stuff but just follow the link in the event javascript is not available.

These methods are a bit more graceful in how they react to the browser not having javascript as they fall back to standard html form behaviour and require no code to detect javascript – it simply ignores your javascript and submits the form as it should.

Regarding checkboxes, be aware that the default behaviour in non-javascript enabled pages is not to post back on changes. If you change the state of a check-box, you always have to hit the submit button to postback, you simply can’t do a postback on checkbox state change without javascript.

Several controls in asp.net (including drop down lists) have the option to auto-postback upon client change, this is done via javascript and if that is not available the only way to gracefully degrade is to have a button that the user clicks to force a standard html postback so your server can respond to the changed control state.

If you find you are struggling to have a coherent ‘flow’ in your UI if you don’t have the auto-postback on checkboxes/combos etc then you might need to rethink your UI design and move to a more wizard-based layout.

I disable auto-postbacks on those types of things anyway as it is horrible for the user, which is a shame as you are going to great lengths to give them a usable experience when their browser is not using javascript.