How to handle multiple return statements

Question

I am trying to restructure a function more clearly and readable that has multiple return statements.

Usecase

Get a token:

if the token does not exist in the database then generate a new one and return it.
if the token exists -check if expired, if expired update it with a new one, -if not expired then return the same token.

Code

 export const GetToken = async () => {
    
        const db = new DB();
    
        const check = await db.GetItem();
    
        if(check.Count === 0) {
            const token = await GenerateToken();
            return token;
        }
    
        if(check.Count >= 1) {
    
            const db_token = check.Items[0];
            const isExpired = isTokenExpired(db_token);
    
            if(isExpired) {
                const token = await UpdateToken(db_token);
                return token;
            }
            return db_token;
        }
    }

There are 3 return statements in this function and there is not a base return function.

The question is basically a good one, but the title was a little too common for code review. The title has been changed to bring it more in line with what is expected on code review. The title should state what the code does rather than what your concerns about the code are, put the concerns in the body of the question. Please see our guidelines, especially the title section. — pacmaninbw
– pacmaninbw ♦, Commented Jun 20, 2020 at 14:04
@pacmaninbw i disagree, its less about returning a token from the database and more about how to handle multiple return statements in a function. — Kay
– Kay, Commented Jun 20, 2020 at 22:32
That title can make the question off-topic, which is why I changed it. — pacmaninbw
– pacmaninbw ♦, Commented Jun 20, 2020 at 22:34
Do you have a goal of changing the function so that it only has one return statement? If so, is there a particular reason why you want to do that? — Sophie Swett
– Sophie Swett, Commented Jun 20, 2020 at 23:48

pacmaninbw · Accepted Answer · 2020-06-20 14:10:47Z

3

I'm no expert in JavaScript, but it seems to me if you changed the scope of token so that it is defined at the beginning of the function and then just modify the value as necessary that you can have only one return statement after all the if statements.

answered Jun 20, 2020 at 14:10

pacmaninbw♦

26.1k13 gold badges47 silver badges114 bronze badges

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SirPython · Accepted Answer · 2020-06-20 14:50:04Z

2

There is some simplification to be done.

The second if statement is superfluous. I'm assuming that if .Count is not 0, then you know it's going to be >=1, so you don't need to write a second if-statement.
You don't need to save variables the values of which you only use once.

export const GetToken = async () => {
  const check = await new DB().GetItem();

  if (check.Count === 0) {
    return await GenerateToken();;
  }

  const db_token = check.Items[0];
  if (isTokenExpired(db_token)) {
    return await UpdateToken(db_token);
  }
  
  return db_token;
}

I'm not all too against having multiple return statements since this is a very short function. For longer functions, having multiple exit points can be confusing. If you do want to have fewer return statements (which is not a bad idea at all), then I agree with pacmaninbw's answer that you could have a single variable at the start of the function, populate that with the return value, and then just return that variable at the end of the function.

export const GetToken = async () => {
  let retToken;
  const check = await new DB().GetItem();

  if (check.Count === 0) {
    retToken = await GenerateToken();;
  }

  const db_token = check.Items[0];
  if (isTokenExpired(db_token)) {
    retToken = await UpdateToken(db_token);
  } else {
    retToken = db_token;
  }
  
  return retToken;
}

(By the way, javascript typically uses camelCase for variable names and not snake_case)

edited Jun 20, 2020 at 14:50

answered Jun 20, 2020 at 14:44

SirPython

13.5k3 gold badges38 silver badges93 bronze badges

\$\begingroup\$ Since you removed the second if statement to check if it is >= 1 you are doing some unnecessary operations such as checking if the token is expired. The assumption is that when you generate a new token it does not need to be checked to see if the token has expired. This was the reason for the second if statement - expiry check can be skipped if a new token was generated \$\endgroup\$

Kay
– Kay

2020-06-20 22:24:58 +00:00
Commented Jun 20, 2020 at 22:24
\$\begingroup\$ given the above i guess i can just add a return refToken = await GenerateToken() \$\endgroup\$

Kay
– Kay

2020-06-20 22:26:37 +00:00
Commented Jun 20, 2020 at 22:26
\$\begingroup\$ For longer functions, having multiple exit points can be confusing I disagree on that point. Multiple return statements make it easier to understand a long function, because once you hit one you know the rest of the function doesn't matter for the branch you took. Your first method is also better because it guarantees you don't return an uninitialized value, while your second method requires you to check every branch to make sure you don't. \$\endgroup\$

Turksarama
– Turksarama

2020-06-21 01:04:22 +00:00
Commented Jun 21, 2020 at 1:04
\$\begingroup\$ @Kay That is fair. I didn't quite understand the system you were dealing with so clearly that is a judgement you needed to make yourself, and I agree entirely with it. \$\endgroup\$

SirPython
– SirPython

2020-06-21 15:17:13 +00:00
Commented Jun 21, 2020 at 15:17
\$\begingroup\$ @Turksarama Interesting perspective. I've read different opinions on multiple exit points versus one single. I like your point of view. \$\endgroup\$

SirPython
– SirPython

2020-06-21 15:17:47 +00:00
Commented Jun 21, 2020 at 15:17

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