You used a return statement in the global scope of your code. The return statement should only appear within the body of a function.
Invoking a function with the () operator is an expression. All expressions have values; the return statement is used to specify the value retuned by a function. The general form is:
return [ expression ];
When the return statement is executed, expression is evaluated and returned as the value of the function. If there is no expression, undefined is returned.
Execution of the function stops when the return statement is executed, even if there are other statements still remaining in the function body. The exception to this rule is if the return statement occurs within a try block, and there is a corresponding finally block, the code in the finally block will execute before the function returns.
If a function returns because it reaches the end of the function body without executing a return statement, the value returned is the undefined value (this means the function result cannot be used as part of a larger expression).
To correct this error
Remove the return statement from the main body of your code (the global scope).