Question

regular = 'a string';
enriched = enrichString(regular);
sys.puts(enriched);

function enrichString(str){
    //run str through some regex stuff or other string manipulations
    return str;
}

Right now it seems to be doing what I hoped it would do but I don’t know if its safe. Could this result in undefined sometimes? Do I need to do something like:

regular = 'a string';
enriched = enrichString(regular, function(data){sys.puts(data);});

function enrichString(str, cb){
    //run str through some regex stuff or other string manipulations
    cb(str);
}

Thanks for the help!

Answer 1

You only need callbacks if your making asychronous non-blocking calls.

var string = "foo",
    new_string = enrich(foo);

doStuff(new_string);

Is safe if enrich is blocking. For example

function enrich(str) {
    // do regex stuff with str

    // manipulate it

    return str;
}

is blocking so it’s safe to do this. Where as

function enrich(str) {
    // get some data from the database.

    // store the string in a file.

    return str;
}

Uses non blocking IO and is not safe. What you want to do is this :

function enrich(str, cb) {
    // get some data from the database.

    // store the string in a file.

    return cb(str);
}

var string = "foo",
    new_string = enrich(foo, function (str) {
        doStuff(new_string);
    });

Notice that

enriched = enrichString(regular, sys.puts(data));

Does not work because your passing in the return value of sys.puts(data) as your function parameter (data is undefined aswell!)

You need to pass in a function.