Question

My JavaScript is pretty nominal, so when I saw this construction, I was kind of baffled:

var shareProxiesPref = document.getElementById('network.proxy.share_proxy_settings'); shareProxiesPref.disabled = proxyTypePref.value != 1; 

Isn’t it better to do an if on proxyTypePref.value, and then declare the var inside the result, only if you need it?

(Incidentally, I also found this form very hard to read in comparison to the normal usage. There were a set of two or three of these conditionals, instead of doing a single if with a block of statements in the result.)

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UPDATE:

The responses were very helpful and asked for more context. The code fragment is from Firefox 3, so you can see the code here:

http://mxr.mozilla.org/firefox/source/browser/components/preferences/connection.js

Basically, when you look at the Connect preferences window in Firefox, clicking the proxy modes (radio buttons), causes various form elements to enable|disable.

Answer 1

It depends on the context of this code. If it’s running on page load, then it would be better to put this code in an if block.

But, if this is part of a validation function, and the field switches between enabled and disabled throughout the life of the page, then this code sort of makes sense.

It’s important to remember that setting disabled to false also alters page state.