Robust Error Handling in TypeScript: A Journey from Naive to Rust-Inspired Solutions

Introduction

In software development, robust error handling forms the foundation of reliable software. Even the best-written code encounters unexpected challenges in production. This post explores how to enhance TypeScript error handling with Rust’s Result pattern—creating more resilient and explicit error management.

The Pitfalls of Overlooking Error Handling

Consider this TypeScript division function:

const const divide: (a: number, b: number) => numberdivide = (a: numbera: number, b: numberb: number) => a: numbera / b: numberb;

This function appears straightforward but fails when b is zero, returning Infinity. Such overlooked cases can lead to illogical outcomes:

const const calculateAverageSpeed: (distance: number, time: number) => stringcalculateAverageSpeed = (distance: numberdistance: number, time: numbertime: number) => {
  const const averageSpeed: numberaverageSpeed = const divide: (a: number, b: number) => numberdivide(distance: numberdistance, time: numbertime);
  return `${const averageSpeed: numberaverageSpeed} km/h`;
};

// will be "Infinity km/h"
var console: Console
The `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
@see[source](https://github.com/nodejs/node/blob/v22.x/lib/console.js)console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```

See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
@sincev0.1.100log("Average Speed: ", const calculateAverageSpeed: (distance: number, time: number) => stringcalculateAverageSpeed(50, 0));

Embracing Explicit Error Handling

TypeScript provides powerful error management techniques. The Rust-inspired approach enhances code safety and predictability.

Result Type Pattern: A Rust-Inspired Approach in TypeScript

Rust excels at explicit error handling through the Result type. Here’s the pattern in TypeScript:

type 
type Success<T> = {
    kind: "success";
    value: T;
}Success<function (type parameter) T in type Success<T>T> = { kind: "success"kind: "success"; value: Tvalue: function (type parameter) T in type Success<T>T };
type 
type Failure<E> = {
    kind: "failure";
    error: E;
}Failure<function (type parameter) E in type Failure<E>E> = { kind: "failure"kind: "failure"; error: Eerror: function (type parameter) E in type Failure<E>E };
type type Result<T, E> = Success<T> | Failure<E>Result<function (type parameter) T in type Result<T, E>T, function (type parameter) E in type Result<T, E>E> = 
type Success<T> = {
    kind: "success";
    value: T;
}Success<function (type parameter) T in type Result<T, E>T> | 
type Failure<E> = {
    kind: "failure";
    error: E;
}Failure<function (type parameter) E in type Result<T, E>E>;

function function divide(a: number, b: number): Result<number, string>divide(a: numbera: number, b: numberb: number): type Result<T, E> = Success<T> | Failure<E>Result<number, string> {
  if (b: numberb === 0) {
    return { kind: "failure"kind: "failure", error: stringerror: "Cannot divide by zero" };
  }
  return { kind: "success"kind: "success", value: numbervalue: a: numbera / b: numberb };
}

Handling the Result in TypeScript

const const handleDivision: (result: Result<number, string>) => voidhandleDivision = (result: Result<number, string>result: type Result<T, E> = Success<T> | Failure<E>Result<number, string>) => {
  if (result: Result<number, string>result.kind: "success" | "failure"kind === "success") {
    var console: Console
The `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
@see[source](https://github.com/nodejs/node/blob/v22.x/lib/console.js)console.Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```

See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
@sincev0.1.100log("Division result:", result: Success<number>result.value: numbervalue);
  } else {
    var console: Console
The `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
@see[source](https://github.com/nodejs/node/blob/v22.x/lib/console.js)console.Console.error(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to `stderr` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const code = 5;
console.error('error #%d', code);
// Prints: error #5, to stderr
console.error('error', code);
// Prints: error 5, to stderr
```

If formatting elements (e.g. `%d`) are not found in the first string then
[`util.inspect()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilinspectobject-options) is called on each argument and the
resulting string values are concatenated. See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)
for more information.
@sincev0.1.100error("Division error:", result: Failure<string>result.error: stringerror);
  }
};

const const result: Result<number, string>result = function divide(a: number, b: number): Result<number, string>divide(10, 0);
const handleDivision: (result: Result<number, string>) => voidhandleDivision(const result: Result<number, string>result);

Native Rust Implementation for Comparison

In Rust, the Result type is an enum with variants for success and error:

fn divide(a: i32, b: i32) -> std::result::Result<i32, String> {
    if b == 0 {
        std::result::Result::Err("Cannot divide by zero".to_string())
    } else {
        std::result::Result::Ok(a / b)
    }
}

fn main() {
    match divide(10, 2) {
        std::result::Result::Ok(result) => println!("Division result: {}", result),
        std::result::Result::Err(error) => println!("Error: {}", error),
    }
}

Why the Rust Way?

1. Explicit Handling: Forces handling of both outcomes, enhancing code robustness.
2. Clarity: Makes code intentions clear.
3. Safety: Reduces uncaught exceptions.
4. Functional Approach: Aligns with TypeScript’s functional programming style.

Leveraging ts-results for Rust-Like Error Handling

For TypeScript developers, the ts-results library is a great tool to apply Rust’s error handling pattern, simplifying the implementation of Rust’s Result type in TypeScript.

Conclusion

Implementing Rust’s Result pattern in TypeScript, with tools like ts-results, enhances error handling strategies. This approach creates robust applications that handle errors while maintaining code integrity and usability.

Let’s embrace these practices to craft software that withstands the tests of time and uncertainty.