Why does (+ + '') === 0?

Question

Can anyone please explain this weird javascript behavior?

+
// Rightfully gets a syntax error, because there are no operands

+ +
// Same as above

+ + ''
// Interpreted as 0

typeof(+ + '')
// Interpreted as "number"

+ + '' === 0
// Interpreted as true

So in other words, (+ + '') is computed as zero. 1) How is that even syntactically allowed? 2) Why does that compute to zero?

Answer 1

The unary plus (+) operator converts the right hand side to a number.

So you have 0 ← 0 ← empty string.