In my opinion, it’s not the sunken cost that is the problem, it’s the fact that we expect stuff to go all lean and have no flaws in the first place. Software is hard and complex and must accommodate hard to implement and complex changes constantly. All this takes more and more money as more and more functionality is desired from the same product. Killing the product and starting all over again will:
a) cost at least as much as is did to get it in the current stage.
b) have to be repeated as many times necessary when new functionality is added in time and the current version becomes bloated.

So, as you can see, there’s money down the drain both ways, the best you can save is some degree of frustration for a while.

I believe another language could displace it, but it would have to be adopted by all the big browser players (Microsoft, Mozilla, Apple, and now Google), and realistically would have to become an official standard to really gain any traction with the web elites. From that point I expect it would be about five years before you started seeing Javascript displaced in significant applications, and even then it would be phased in alongside Javascript rather than replacing it 100% at once.

Kind of like the other comment regarding not throwing out decades-old legacy code. Because by that point, Javascript WILL be a “decades old” language… :)

One point that I’d like to add is that we often tend to overestimate how much of the cost is sunk into the code itself. The most expensive part of developing software is gaining a deep understanding of both the problem and the solution domains.

If you still have those people with the understanding, then a code re-write would be significantly cheaper. For a complex decades-old system, the cost of gaining a deep and broad understanding would be huge. The evolution of those systems tends to slow more and more until they are replaced by a revolution.

BTW, I agree with your javascript example (and HTML for that matter) but I find the more interesting debate is around if/when/how to re-write.

Joel’s article is also somewhat one-sided, but his points are valid, and this was a tidy way to put the reason for the skewed evaluations: “It’s harder to read code than to write it.”

The proper way to “throw away” a huge, ugly mess of code in most cases is to refactor it gradually into non-existence, not throw it away first and *then* see if you can reproduce functionality you may not have even fully understood.

Another way to put it — the sunk cost fallacy absolutely applies to software development decisions, and if you have access to *reliable* estimations of effort required for the various different options, the decision is easy (and every once in a while it’ll be the right thing to jettison an entire codebase). But if you rely on the little-more-than-gut estimates (and natural excitement at starting fresh, with noble aims of “doing it right this time”…), sometimes you’re really going to suffer in the long run… and due to budget overruns, last-minute hacks, desperate fixes, etc. after a few years your new project will be just as much an ugly mess as the one you replaced (but that ugly mess exchange will have been so very much more expensive than working to clean up the first mess…).

You mentioned day-to-day throwing away of code in a comment below — that’s great; that’s refactoring, and that’s the real secret to good architecture & code, not starting from scratch every time it feels like a good idea.

[reading more comments... apologies if I'm just rewording John's points too much here]

But like x86 assembly, the people who have to write in it tend to defend it. And they can show you cool stuff that can be done with it (I did some really cool stuff with Logo when I was 6), but it doesn’t change the fact that Javascript violates several of the key tenets of a good language. Such as basic things should be easy. Simple mistakes should be hard to make. Difficult things should be possible. Of these Javascript really only satisfies the last one.

What people hate is JavaScript and the DOM. That’s what sucks.