10 TypeScript Error Handling Best Practices

TypeScript is a typed superset of JavaScript that compiles to plain JavaScript. It offers classes, modules, and interfaces to help you build robust components. TypeScript is widely used for Angular development.

Error handling is an important part of any programming language. In TypeScript, errors are thrown when the compiler encounters an issue. TypeScript provides a few ways to handle errors. In this article, we will discuss some best practices for error handling in TypeScript.

1. Don’t use any

The any type is a powerful way to opt-out of type checking. It tells the TypeScript compiler to trust you and not second-guess your code. While that may be what you want sometimes, it’s almost always a bad idea.

The reason is that any disables all type safety checks. That means TypeScript will allow you to do things that are usually considered errors, like accessing properties that don’t exist or calling functions with the wrong number of arguments.

Not only does this make your code more likely to have bugs, but it also makes it harder to refactor and maintain. Any should be used sparingly, and only in cases where you’re confident that the type checker is getting in your way.

2. Use try/catch blocks to catch errors

When an error is thrown, it’s important to have a way to catch it so that the program can continue running. Try/catch blocks provide this functionality by allowing you to specify code that should be executed if an error is thrown, as well as code that should be executed if no error is thrown.

This is especially important in TypeScript because of its strict type checking. If an error is thrown and not caught, the program will immediately stop running. This can be frustrating for users, so it’s important to catch errors whenever possible.

Try/catch blocks are also useful for logging purposes. By catching and handling errors, you can log the details of the error and help debug the issue. This is especially helpful when working with large projects with many different dependencies.

3. Use the Error object

The Error object provides valuable stack trace information that can help you debug your code. It also gives you a standard way of representing errors that can be used across different programming languages and platforms.

If you’re not using the Error object, you’re missing out on important debugging information and you’re making it harder to interoperate with other programming languages.

4. Throw your own errors

When you throw your own errors, you can be sure that the type of error is always correct. This means that you won’t have to waste time debugging TypeScript type errors.

Furthermore, throwing your own errors allows you to add context to the error message. This is especially useful when dealing with asynchronous code, where it can be difficult to figure out what went wrong and where.

Finally, by throwing your own errors, you can ensure that the stack trace always points to the original source of the problem. This makes debugging much easier and faster.

5. Catch and rethrow an error

If you have a try/catch block and you catch an error, the default behavior is for the error to be thrown away and execution continues on. This can lead to subtle bugs because the code that follows the try/catch block may be expecting that an error was thrown and handled.

Instead, it’s best to catch the error and then rethrow it. This way, execution will stop at the point where the error was caught, and the caller of the function will be able to handle the error.

6. Use a finally block

A finally block is executed whether or not an exception is thrown. This means that you can put cleanup code in a finally block, such as closing a file or database connection, regardless of whether an error occurred.

If an error does occur, the finally block code is still executed before control is returned to the caller. This means that you can use the finally block to log the error, even if the try/catch block has already handled it.

The finally block is also executed if the program exits the try block by executing a return statement.

7. Use async/await

Async/await is a new way to write asynchronous code. It’s available in TypeScript 2.1 and higher. Async functions are declared with the async keyword. The await keyword can only be used inside an async function.

Async/await makes asynchronous code look and feel like synchronous code. This is why it’s so popular. It makes code easier to read and debug.

With async/await, you can handle errors in a much cleaner way than with traditional try/catch blocks. When an error occurs in an async function, it will be caught by the nearest enclosing try/catch block.

If there is no enclosing try/catch block, the error will be thrown all the way up to the global scope. This can be useful for debugging purposes. But it can also lead to unhandled promise rejections, which can be hard to debug.

To avoid this, always make sure to add a top-level try/catch block around your async code.

8. Use promises

When you use promises, you can be sure that your code will execute in the order that you expect it to. This is because promises always execute asynchronously, which means that any code that comes after a promise will not execute until the promise has been resolved.

This can be extremely helpful when you’re dealing with complex code that relies on data from multiple sources. By using promises, you can be sure that all of the data that your code needs will be available before the code executes.

Additionally, promises make it easy to handle errors. If an error occurs within a promise, it will be automatically caught and returned as a rejected promise. This makes it much easier to debug your code, as you don’t need to worry about manually catching and handling errors.

9. Handle promise rejections

A promise rejection means that an error occurred while the async operation was being executed. This can happen for a variety of reasons, ranging from network issues to programming errors.

If you don’t handle promise rejections, your program will continue executing even though an error occurred. This can lead to unexpected behavior and can even cause your program to crash.

To avoid these problems, always add a .catch() handler to your promises. This way, you can gracefully handle any errors that occur.

10. Use for…of loops

for…of loops offer a few advantages over for…in loops. For one, they’re more concise. They also don’t require you to use an indexer. And finally, for…of loops can’t be used with objects. So if you’re working with arrays—which is a data type that’s often used in conjunction with TypeScript—for…of loops are the way to go.