Making Clean Code: Testing Concurrency and Error Handling
When it comes to writing clean code, there are several key principles to keep in mind. One of the most important is testing. It's always good to strive for 100% test coverage of your code. This means that every line of code should have at least one test associated with it.
The Use of a Single Concept per Test
There's an example provided in the transcription of a bad way of writing tests. The test is trying to test three different things: handling 30-day months, leap years, and non-leap years. This is a problem because callbacks aren't clean and they can cause a lot of nesting. In contrast, using a single concept per test makes the code much cleaner and easier to understand.
The Problem with Callbacks
Callbacks aren't clean and they cause a lot of nesting. They're often used when working with asynchronous code, but they can lead to a lot of complexity in the code. In this example, we see callbacks being used to get the free Code Camp Wikipedia page, write a file, and log the written file all in a row. This is a problem because it's difficult to read and understand.
The Solution: Using Promises
So what can we do instead? The solution is to use promises. Promises are a built-in global type that allows us to handle asynchronous code in a much cleaner way. Instead of using callbacks, we can use the dot notation and the `do-then` function to write our code.
Using Promises for Asynchronous Code
Here's an example of how you might use promises to get the free Code Camp Wikipedia page, write a file, and log the written file:
```
fetch('https://en.wikipedia.org/wiki/CodeCamp')
.then(response => response.json())
.then(data => {
const content = data['Content'];
const title = 'Code Camp Article';
const filename = `codecamp-${Date.now()}.txt`;
fs.writeFileSync(filename, content);
console.log(`File ${filename} written successfully.`);
})
.catch(error => {
console.error('Error occurred:', error);
});
```
As you can see, this code is much cleaner and easier to understand than the original example using callbacks.
The Benefits of Using Async/Await
But promises aren't the only way to write clean asynchronous code. With the introduction of async/await in ES8, it's now possible to write even cleaner code that's easier to read and understand.
Async/Await for Cleaner Code
Here's an example of how you might use async/await to get the free Code Camp Wikipedia page, write a file, and log the written file:
```
async function main() {
try {
const response = await fetch('https://en.wikipedia.org/wiki/CodeCamp');
const data = await response.json();
const content = data['Content'];
const title = 'Code Camp Article';
const filename = `codecamp-${Date.now()}.txt`;
fs.writeFileSync(filename, content);
console.log(`File ${filename} written successfully.`);
} catch (error) {
console.error('Error occurred:', error);
}
}
main();
```
As you can see, this code is even cleaner and easier to understand than the previous examples using promises.
Handling Errors
When working with asynchronous code, it's often necessary to handle errors. This means that we need to do something when an error occurs, rather than just letting it propagate up the call stack.
The Problem with Ignoring Caught Errors
One common mistake is to ignore caught errors. This can happen if we don't properly log or report the error, or if we don't take any action to recover from the error.
Using console.error for Error Reporting
In the past, `console.log` was often used for error reporting. However, this isn't always the best approach. Sometimes, it's necessary to use `console.error` instead of `console.log`.
The Benefits of using console.error
Here are some benefits of using `console.error` for error reporting:
* `console.error` logs errors in a different color and with more detail than `console.log`.
* It provides better feedback on what went wrong.
* It allows you to take action when an error occurs, rather than just ignoring it.
Reporting Errors to the User
In addition to logging or reporting errors internally, we may also want to report them to the user. This can be done using various means such as email notifications, in-app alerts, or even messaging services like Twilio.
Conclusion
Making clean code is essential for writing efficient, maintainable, and scalable software systems. By following best practices for testing, concurrency, error handling, and code organization, developers can write cleaner, more readable code that's easier to understand and modify.
In conclusion, this article has explored the key principles of making clean code using promises and async/await for writing asynchronous code in JavaScript.