The expression +'42' evaluates to the number 42. The unary plus operator (+) attempts to convert its operand to a number. When applied to a string that contains a valid numeric representation, it converts the string to the corresponding number. This is a shorthand for Number('42') and is an example of explicit type conversion, although it uses operator syntax rather than a function. The unary plus is often used as a concise way to convert strings to numbers.