The parentheses ( ... ) around the assignment statement are required when using object literal destructuring assignment without a declaration. {a, b} = {a: 1, b: 2} is not valid stand-alone syntax, as the {a, b} on the left-hand side is considered a block and not an object literal.

Your ( ... ) expression needs to be preceded by a semicolon or it may be used to execute a function on the previous line.