Message
Warning: unreachable code after return statement (Firefox)
Error Type
Warning
What went wrong?
Unreachable code after a return statement might occur in these situations:
- When using an expression after a
return
statement, or - when using a semicolon-less return statement but including an expression directly after.
When an expression exists after a valid return
statement, a warning is given to indicate that the code after the return
statement is unreachable, meaning it can never be run.
Why should I have semicolons after return
statements? In the case of semicolon-less return
statements, it can be unclear whether the developer intended to return the statement on the following line, or to stop execution and return. The warning indicates that there is ambiguity in the way the return
statement is written.
Warnings will not be shown for semicolon-less returns if these statements follow it:
Examples
Invalid cases
function f() { var x = 3; x += 4; return x; // return exits the function immediately x -= 3; // so this line will never run; it is unreachable } function f() { return // this is treated like `return;` 3 + 4; // so the function returns, and this line is never reached }
Valid cases
function f() { var x = 3; x += 4; x -= 3; return x; // OK: return after all other statements } function f() { return 3 + 4 // OK: semicolon-less return with expression on the same line }