Introducing the Safe Assignment Operator in JavaScript

George Wilde
3 min readOct 10, 2024

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Photo by Artem Sapegin on Unsplash

I love seeing improvements to the core JavaScript language that positively impact the developer experience, and there’s no better place to look for improvements than in handling errors. The proposal of the Safe Assignment Operator ?= should be a significant upgrade that makes the life of developers just that little bit easier.

This new ECMAScript proposal https://github.com/arthurfiorette/proposal-safe-assignment-operator aims to streamline the handling of errors, making your code cleaner and more efficient by reducing the need for good old try-catch blocks. Inspired by error-handling patterns in other programming languages, the Safe Assignment Operator brings a fresh approach to managing errors in JavaScript. Let’s take a look at how it works 😀

Why the Safe Assignment Operator is Useful

Simplified Error Handling

Traditional try-catchblocks often lead to deeply nested code, making it harder to read and maintain. The Safe Assignment Operator addresses this by transforming the result of a function into a tuple. If an error occurs, it returns[error, null]; otherwise, it will return [null, result]. This reduces the need for nestedtry-catchblocks, making your code more readable and maintainable.

Imagine you’re fetching data from an API. Instead of wrapping your code in multiple layers oftry-catch, you can handle errors more gracefully and keep your code clean and straightforward.

async function getData() {
const [error, response] = await fetch("https://api.example.com/data");
if (error) return handleError(error);
return response;
}

Enhanced Readability

Try-catchblocks can clutter code and disrupt the flow of logic. The Safe Assignment Operator makes error handling more intuitive, keeping your code linear and easy to follow.

Picture this: you’re working on an asynchronous function, and instead of breaking the flow withtry-catch, you handle errors seamlessly, streamlining your code.

const [error, data] = await someAsyncFunction();
if (error) handle(error);

Consistency Across APIs

Different APIs might require different error-handling techniques, leading to inconsistencies. The Safe Assignment Operator introduces a consistent way to handle errors across all APIs, ensuring uniform behaviour.

Think of it as having a universal remote for all your devices. No more fumbling around with different remotes; just one smooth, consistent experience.

Recursive Error Handling

The Safe Assignment Operator can recursively handle nested objects that implementSymbol.result, ensuring even complex error scenarios are managed smoothly.

const obj = {
[Symbol.result]() {
return [
null,
{ [Symbol.result]: () => [new Error("Nested error"), null] }
];
},
};
const [error, data] = obj;

Promises and Async Functions

The Safe Assignment Operator is designed to work seamlessly with Promises and async/await, making error handling in asynchronous code straightforward.

Imagine you’re on a road trip, and instead of stopping at every checkpoint to check for errors, you have a smooth, uninterrupted journey.

const [error, data] = await fetch("https://api.example.com");

Why Not Data First?

Placing the error first in the[error, data]structure ensures that errors are handled before processing data, reducing the risk of ignoring errors.

const [error, data] = someFunction();

Conclusion

The Safe Assignment Operator proposal is a promising addition to JavaScript. It simplifies error handling and enhances code readability. Who doesn’t want more of that in their life? 🧘‍♂️

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George Wilde
George Wilde

Written by George Wilde

Tech Leader, Principal Engineer and Builder of Things

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