One key point to consider is the importance of designing your modules in a way that asynchronous functions do not throw errors to catch, but rather are handled within a callback function. Take for example the fs.readdir method you provided...
The recommended approach to design your module is illustrated below:
var example = {
logString: function(data, callback){
var err = null;
if (typeof data === "string") {
console.log(data);
} else {
err = {"message": "Data is not a string!"};
}
callback(err);
}
}
The idea behind this structure is to allow the end user to manage any potential errors inside the callback function instead of resorting to a try/catch block. For instance, when utilizing the example object:
example.logString(123, function(err){
// Error handling takes place within the callback
if (err) console.log(err)
});
In this scenario, the message
{"message": "Data is not a string!"}
would be logged because the data does not match the expected
typeof value of
"string".
An example of what should be avoided:
Avoid throwing errors when working with asynchronous callbacks. Consider a redesigned version of the logString method where an error is thrown instead of passed to the callback function:
var example = {
logString: function(data, callback){
if (typeof data === "string") {
console.log(data);
} else {
throw {"message": "Data is not a string!"};
}
callback();
}
}
With this setup, you must utilize a try/catch block to handle errors:
try {
example.logString(321, function(){
console.log("Done!")
});
} catch (e) {
console.log(e)
}
Final thoughts / Summary:
NPM recommends this coding approach as it offers better manageability within asynchronous methods.
NodeJS and JavaScript tend to favor asynchronous environments, making it advantageous to consolidate error handling within the callback function.
By avoiding unnecessary try/catch blocks and incorporating error handling directly into the callback, you can streamline your code and ensure smoother asynchronous execution.