immutable-parsejs

immutable-parsejs

Sometimes when working with large data sets that come from an external source, think API, we need someway of converting that data into Immutable structures. This is useful, not only for type safety, but also for comparison checks and the improved performance they provide.

For more on why, check out Immutable's documentation: https://immutable-js.com/

This package (389 bytes GZipped) exports a single function, parseJs, that can be used to wrap a nested data structure in Immutable objects, namely List and Record.

Getting Started

Install with Yarn:

$ yarn add immutable-parsejs

Install with NPM:

$ npm i immutable-parsejs

Using parseJs()

Once you have your data structure, either an object, or an array of objects, you can pass that into the parseJs function:

import { parseJs } from 'immutable-parsejs';

const dataSet = [
  { userId: 1001, firstName: 'John' },
  { userId: 1002, firstName: 'Joe' },
];

const result = parseJs(dataSet); // <-- List<Record>;
const { firstName } = result.get(0);

/*[...]*/

console.log(firstName); // <-- John

/*[...]*/

console.log(result === result.setIn([0, 'firstName'], 'John')); // <-- true
console.log(result === result.setIn([0, 'firstName'], 'Sam')); // <-- false

Now your data set is wrapped recursively, objects will now be Record's, and arrays will be List's.

Known issues

When working with complex structures in TypeScript, getting nested types to work is tricky. Types are automatically infered, but they can only do so much. If you have an array of objects, that themselves have arrays, TypeScript will incorrectly infer the arrays within an object to be array primitives, not List's. To get around this, I'd suggest that you define your data structure via an interface upfront (this is good practice, anyway).