Earlier quoted context omitted.
Any particular reason why you feel like server-side JavaScript feels fragile? Also if by DOM manipulation you mean libraries like jQuery, have you tried more declarative approaches found in frameworks like Angular and React?
Few reasons: 1. Cooperative multitasking. Really? In 2014? Hello? 2. Weakest of weak typing. undefined is not a function? Anyone? 3. Everyone can override everything. 4. Conventions, that's the only way you can build software in JS. Anyone know of a person who doesn't break conventions? Having programmed in something like Erlang, which IMHO is the sanest technology available today for doing web, JS feels horrible.
2. Weak typing is a nice feature for prototyping, but for larger projects, a stronger type system is better at catching bugs. Many JavaScript programmers (myself included) are used to using separate systems to check types for them. My team uses the Closure Compiler, which, along with compiling the JS to a more optimized version, is also happy to check all your types and fails to build if your types don't line up.
3. Again, I believe this is something that you can make sure that the compiler catches. And, of course, anyone can write bad code (in any language); if you're overwriting stuff halfway across the codebase, then that's "bad code" and you should avoid doing that (and during the code review stage, you should be making sure that your coworkers don't do that either).
4. Like for any language, have guidelines for how you write code, and enforce some of your conventions with the compiler and with linting tools. It leads to a more consistent codebase.