This next item isn't a language feature, it's a technique.
Have you ever had your brain explode looking at code like this?
function MySomething () {
if ((x=1) || (y-2)) {
for (var i=0; i<10; i++) {
if (a>b) {
DoAnotherSomething()
}
else {
switch (important) {
true: thing()
false: otherthing()
}
}
}
}
}
All those closing curly-brackets are somewhat impenetrable. If you happened to code it perfectly first time, then great. But if you need to fix an error, this gets really hard for humans to look at.