behaviour of + operator depends on types of operands

[michaelficarra]

+ can mean either addition or string concatenation depending on its operands. And if neither operand is a literal (a + b), it becomes a chore to figure out which behaviour is being denoted. In the most extreme cases, one can't even statically determine this. This leads to accidental addition being a common bug even among experienced ECMAScripters.

[DavidBruant]

What would be the associated good practice?
Always coerce to the expected type (string xor number) before using +?

Thanks for your contribution. I'm glad ECMAScript Regrets can be of some help in other projects ;-)

[michaelficarra]

When intending to do string concatenation, start with an empty string literal. So a + b becomes "" + a + b. When intending to do addition, prefix each operand with a unary plus: +a + +b. That one may get a little tedious.