How to avoid duplicate code blocks in node.js

Question

I have a code block containing if else and most of the code in if and else is same, but due to one function call with callback, I have to quite a same code in both if and else block. I know a function can be created for this purpose but it will require me to pass too many paramaters. Here is the code block:

if (results[0].register_type == 'D') {
                sessionData.register_type = results[0].register_type;
                UserModel.updategcm_id(req.body, function (err, result) {
                    UserSessionModel.createSessionToken(sessionData, function (err, result, token) {
                        if (err) {
                            res.status(400).send(self.createResponse({}, {
                                success: false,
                                message: err.message
                            }));
                            return false;
                        }
                        res.status(200).send(self.createResponse({
                            token: token,
                            userid: results[0].id
                        }, {
                                success: true,
                                message: "User has logged in successfully"
                            }));
                        console.log("User has logged in successfully...\n");
                    });
                });
            } else {
                UserSessionModel.createSessionToken(sessionData, function (err, result, token) {
                    if (err) {
                        res.status(400).send(self.createResponse({}, {
                            success: false,
                            message: err.message
                        }));
                        return false;
                    }
                    res.status(200).send(self.createResponse({
                        token: token,
                        userid: results[0].id
                    }, {
                            success: true,
                            message: "User has logged in successfully"
                        }));
                    console.log("User has logged in successfully...\n");
                });
            }

Why don't you just create a function and pass err, results and token to it? — Seonixx
– Seonixx, Commented Jul 1, 2016 at 9:58
@Seonixx: Actually he already is creating that very function. (twice). — Bergi
– Bergi, Commented Jul 1, 2016 at 10:09

Bergi · Accepted Answer · 2016-07-01 10:15:37Z

1

I think that the best solution is to move the repeated function to a function declaration and just pass it as callback. Your code would change to:

if (results[0].register_type == 'D') {
    sessionData.register_type = results[0].register_type;
    UserModel.updategcm_id(req.body, function (err, result) {
        UserSessionModel.createSessionToken(sessionData, validateResponse);
    });
} else {
    UserSessionModel.createSessionToken(sessionData, validateResponse);
}

function validateResponse(err, result, token) {
    if (err) {
        res.status(400).send(self.createResponse({}, {
            success: false,
            message: err.message
        }));
        return false;
    }
    res.status(200).send(self.createResponse({
        token: token,
        userid: results[0].id
    }, {
        success: true,
        message: "User has logged in successfully"
    }));
    console.log("User has logged in successfully...\n");
}

The code is much more clean now.

You could also factor out the whole createSessionToken call into a function, but you'd have to be careful with passing sessionData, self and res (depending on their respective scope).

edited Jul 1, 2016 at 10:15

Bergi

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answered Jul 1, 2016 at 10:03

miquelarranz

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2 Comments

Bergi Over a year ago

You might need to bind self depending on the scope in which you put validateResponse.

miquelarranz Over a year ago

You are right, but it depends of the rest of the code. I will edit the response, thanks!

Garima · Accepted Answer · 2016-07-01 10:18:48Z

0

You may use async module, so that you don't need to repeat the function.

answered Jul 1, 2016 at 10:18

Garima

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2 Comments

Piyush Arora Over a year ago

Can you point out where exactly I should look in the async documentation: caolan.github.io/async/docs.html ? I am not sure what should I search in the docs.

Garima Over a year ago

Do npm install --save async, then require the module in your server file. After that follow the link.

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