#vanilla javascript
James Sinclair
Sep 15, 2021 ⋅ 18 min read

Using the JavaScript Either monad for error handling

James Sinclair I am passionate about functional programming, test-driven development, and continuous delivery. I am also interested in neural networks and deep learning.

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5 Replies to "Using the JavaScript Either monad for error handling"

  1. Honestly I don’t like this approach for handling errors/exceptions, for me it’s better to read this:

    async function read(id, db) {
    let category = null;

    try {
    category = await db.models.Category.findByPk(id);
    } catch (error) {
    return { success: false, data: null, error: error };

    return { success: true, data: category, error: null };

    router.get(‘categories/:id’, function (req, res, next) {
    let result = await read(req.params.id);
    if (result.success) {
    } else {

    Here I’m handling the possible exceptions successfully, the function will always return a value that’s an object with the flag of “success” as true or false to later do the proper work using the data or the error object.

    I see a better error handling there using a procedural style than trying to figure out what a external dependency that have a flat, left, Ap, right, either, chain etc functions will do for me, I don’t see the intentions of the code clearly, in the procedural way I see the solution easy.

    1. Hi James, thanks for pointing that out. I’ve fixed the formatting for the `Left` and `Right` blocks and have done a bit of extra cleanup as well. Cheers

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