immutable-js VS typescript-eslint

immutable for JavaScript.

Check out Object.freeze. There's also Immutable.js for working with immutable data.

Use immutability to manage state updates When updating state in your React application, it's important to ensure that you are not mutating the original state object. Instead, you should create a new copy of the state object with the updated values. Immutability makes it easier to manage state updates and ensures that the updates are performed in a predictable and safe manner. Libraries like Immutable.js provide a set of functions that simplify working with immutable data in React applications.

We're wanting to get rid of immutable so I'm trying to replicate what it is about the Record functionality and types that allow this dynamic property access to work. After pulling my hair out looking through the [email protected] type definitions and the actual code, to me it looks like the types are just kind of lying about what's going on ... and it's just working. Does anyone have any ideas how I can replicate this dynamic property access with strong typings?

The Immutable.js README has a much more complete description of immutability and why you might want to use the library. Also worth mentioning that Immer is an alternative which is a bit easier to get started with.

Examples: immutable-js Immer

I can't speak to C# and Java, but the suggestion in this post: ImmutableJS already uses Persistent data structures. (It's the second sentence of their introduction)

Avoiding mutation is just never modifiyng an object, ever. There are tons of implementations of this pattern, notably immutable.js (https://immutable-js.com/), Redux is also an example of this philosophy.

JavaScript is most programers' first introduction to map, filter, and reduce. Easy lambdas made those higher-order functions a staple of a lot of JS code.

Meanwhile, immutable.js[0] is at 10 million downloads per week and rising.

I would add that it's not just the ease of use of lambdas, but the fact that in JavaScript functions really are first class citizens. Most of the other widely used languages that people start on have lambda functions added in as a bit of a hack and only treat some functions as real values.

[0] https://www.npmjs.com/package/immutable

Typescript-eslint can assist in this task. This tool helps identify all instances of unsafe any usage. Specifically, all usages of JSON.parse can be found and it can be ensured that the received data's format is checked. More about getting rid of the any type in a codebase can be read in the article Making TypeScript Truly "Strongly Typed".

> Only lint files that have changed? How hard that is?

Quite hard, especially since type-aware rules from e.g. https://typescript-eslint.io/ mean that changing the type of a variable in file A can break your code in file B, even if file B hasn't changed.

The article only touches this: when converting to TypeScript, `any` is useful, but in the end you don't want this type in your codebase - so don't forget to use typescript-eslint [0] and turn on those no-unsafe-* rules which guard against `any` leaking into your code.

[0] https://github.com/typescript-eslint/typescript-eslint

By convention, React components should be named in PascalCase. @typescript-eslint has the config we need, and though we can't specifically target React components, we can target variables (and set some other conventions while we're at it):