CODEWITHSUNDEEP
javascriptnode.jsfunctionparametersundefined
Rympau
Rympau

Reputation: 234

JavaScript: handling undefined as parameter - are those solutions equal?

I would like to know your opinion about below solution. In node.js I often see error handling this way:

        async.each(context.areas, capacityOfArea, function(error) {
            if (error) {
                next(error);
            } else {
                next();
            }
        });

It's often OK, but sometimes it obscures the code (in my opinion) and I would like to simplify this. Does below code equal?

        async.each(context.areas, capacityOfArea, function(error) {
            next(error||undefined);
        });

Upvotes: 0

Views: 166

Answers (2)

Felix Kling
Felix Kling

Reputation: 816364

They could be the same, depending on how next is handling its arguments. But technically they are not the same. In the first case, you are not passing an argument at all, so inside next, arguments.length will be 0. In the second case, you are always passing an argument, so arguments.length will be 1.

Again: Whether or not both produce the same behavior depends on the implementation of next. Most likely yes.

Probably the best way to write this code would be

async.each(context.areas, capacityOfArea, next);

Upvotes: 2

Andras
Andras

Reputation: 3055

Yes, they are the same. Think about what the caller sees -- would next() be able to distinguish next() from next(undefined)?

But taking it one step further, all async cares is whether the error is truthy, it accepts undefined or false or null as success indicators too. And error will either be truthy (an error), or not truthy. If not truthy, we want to call next(<not truthy>), and if error, we want to call next(error), which leads to

async.each(context.areas, capacityOfArea, function(error) {
    next(error);
}

Upvotes: 2

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