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This guide will help you learn and migrate to Elm with assumption you already know the basics of React. The Elm guide is great and will give you a thorough understanding of everything you need to know, in a good order.

This guide is different. Instead, we’re going to start with the fundamentals of JavaScript & React, and how you’d do the equivalent, if any, in Elm. If you already know React, we’ll use those firm groundings so you can feel more comfortable understanding “what Elm means” when they say something using language and concepts familiar to React developers.

Introduction

You can’t use ReScript to call ReScript incorrectly because the compiler will help you make it correct. You can’t use ReScript to call JavaScript wrong because the compiler will help you make it correct.

However, when JavaScript calls your ReScript library, it can do it incorrectly because JavaScript has no compiler; you just run it. This can ruin all the benefits of ReScript: null pointers, runtime errors, and super strange internal ReScript standard library errors that make no sense with stack traces that are not helpful.

Instead, the better thing to do is check the types at runtime, and if wrong, provide helpful runtime errors with what the JavaScript developer needs to do to fix the error. If you’re a ReScript developer providing libraries for JavaScript developers, this article is for you.

Dare Obasanjo on Twitter posts this meme & writes:

A genuine problem in tech is that we’ve created a culture where people switch jobs too often to experience the consequences of their product & technical decisions let alone have to fix them.

I have a new appreciation for Lenses in typed languages. When you learn parsing untyped data like JSON to strong/soundly typed data, Lenses seem wrong.

When you’re presented with 1,000+ of dynamically shaped JSON data you can’t predict, typed Lenses suddenly are The Solution.