+ + what kind of grammar is this?

+Can turn back into numbers (Number type).
!Is to reverse the boolean type.
Specifically, we need to see what we are doing.
I don’t know why I want to change so much.

!+'test'// true
!'test' // false
!+'0' //true
!'0' // false

+Is to let strings become numeric types.
！It is the opposite.

Look at specific fields for understanding.
Here it should be to determine if a value is 0.