Is "return;" necessary/helpful when using callbacks in Node.JS?

Question

For example, are these two effectively the same?

someFunction(val, callback){
    callback(val);
};

and

someFunction(val, callback){
    callback(val);
    return;  // necessary?
};

Answer 1

While they are the same, you will see something like the following from time to time:

someFunction(val, callback){
  if (typeof val != 'object')
    return callback(new Error('val must be an object'));
  callback(null, val);
};

In other words, return is used to "break" out of the function early. Most often, I've seen that used with conditionals; you test for an error condition (returning the callback early if there is an error), then avoid having to wrap the remainder of the function in an else clause.

Answer 2

Yes, they are the same. If your function does not return a value then you can either omit the return statement or use it with no argument; in both cases a call to the function returns "undefined".

function f1(){};
typeof(f1()); // => "undefined"

function f2(){return;};
typeof(f2()); // => "undefined"