General pitfalls across languages
Whether 2 + 2 = 4 is never as simple as it might seem...
Asynchronous code pitfalls
Using Promises incorrectly Not respecting the order of code execution can have unexpected result...
Null comparisons and falsey values
Some languages have weird rules for null comparisons and falsey values; try to keep that in mind ...
Passing by value vs reference
In some languages, you have to pay attention to using variables from a greater scope (e.g. a glob...