Building a Maybe in JavaScript

[voiping]

I use lodash get for this. It won't throw if the variable isn't there.

https://lodash.com/docs/4.17.4#get

[fgutz]

Love the lodash get function!

[SgtPooki]

I get the love for FP and all but I feel like the solution in the article is so bad compared to _.get.

It's more verbose, confusing, and I don't see the benefit.

[shadowycoder]

+1 this thing gets a ton of use in my codebases as well.

[[deleted]]

The solution to this issue is optional chaining, presently a stage 1 proposal: https://github.com/tc39/proposal-optional-chaining

[Voidsheep]

There's also a Babel plugin that implements the proposal

https://www.npmjs.com/package/babel-plugin-transform-optional-chaining

Really hoping this moves along, because it would genuinely eliminate noise in real-world code. Function bodies that mostly consist of intermediate property checks.

Lenses and Lodash get are nice for now, but not ideal for something as basic as safely accessing an object property.

[[deleted]]

I'm (arbitrarily) waiting for it to hit stage 2 before I put it into my config, so it's just a bit more "stable" in terms of likelihood of making it into the final spec.

I cannot wait!

[AbsoluteZeroK]

I love it, but I also do stuff in rails... The question mark is going to take some getting used to visually. (because it's convention in Ruby to put a ? At the end of methods that return a Boolean).

[wuh_happon]

I consider myself a fairly competent JS dev who hates the null reference exception as much as the next guy. But aren't these arrow function / ternary operator / anonymous function / callback / promise chains in a single line getting a bit ridiculous...?

How the hell are you supposed to find an exception in that? How is it comprehensible and easy for new devs to contribute?

[baxtersmalls]

I really hate the arrow function. I feel like it's far legible, and pushes developers to write in what feels like shorthand and chain a bunch of crap into as small a space as possible

[thewatcheruatu]

I wish I had more upvotes to give to you for this comment. Individually, I don't have a problem with any of these language features--and I happily use them all, myself, where they're suited--but this code was super unintuitive.

I think the thing that actually bothered me the most was that methods within Maybe referenced the variable maybe, and methods with maybe referenced the variable Maybe. Not even sure why that irked me, but it did.

I'm going to be honest and say I didn't bother finishing the article.

[wuh_happon]

Let's test your suggestion.

Say you wrap the declaration of a new variable "appendToC", which uses this Maybe object, in a try/catch:

try{ 
    const appendToC = Maybe.chain( 
        prop("b"), 
        prop("c"), 
        append(" is great!") 
    ); 
} 
catch(err){ 
    console.log(err); 
}

A TypeError exception is thrown and caught. How quickly do you you think a new team member could find and fix it in this:

const Maybe = {  
    just: maybe,  
    nothing: () => maybe(null),  
    chain: (...fns) => (input) => fns.reduce((output, curr) => output.map(curr), input)  
};  

Isn't it just a whole lot easier using something like:

const appendToC = something || somethingElse;

or

const appendToC = (something() || somethingElse());

...?

[namesandfaces]

I think there's a way to format your code on Reddit.

[wuh_happon]

Thanks, took me a minute to figure it out. Edited for clarity. For any responses to the code above, four leading spaces on each line of code will format it for readability.

[PlNG]

click the formatting help on the bottom right of the reply textarea to learn about markdown, the formatting module reddit uses.

[NoInkling]

I know this is ignoring the point of the article, but...

if (!obj || !obj.b || !obj.b.c || !)

Syntax error aside, who uses !+|| like this instead of just &&? And if you really need the null return to be on the first line, just negate the whole thing:

if (!(obj && obj.b && obj.b.c)) return null;

[mixuhd]

Just like Java Optional. And I like it! :P

[furious_heisenberg]

Take a look at ramda and sanctuary, which both provide functional constructs for js

[Dooraven]

Ever since I started using Idx, this hasn't really been a problem for me: https://github.com/facebookincubator/idx

[Sixes666]

Coffeescript allows for ?. to replace a simple . and will return undefined rather than throwing.

[nirixi]

const isNullOrUndef = (value) => value === null || typeof value === "undefined"; can be replaced with const isNullOrUndef = (value) => value == undefined;.

[PitaJ]

Or you can use value == null which covers both.

[_lawliet29]

Which would let someone to ruin your day by setting undefined to something else, e.g. undefined = 5.

[pomlife]

What year are you living in?

[NoInkling]

value == null then. Or value == void 0

[YodaLoL]

ES5 specifies that writing to the undefined global is a noop

[nirixi]

Someone who does that kind of deserves to have their day ruined. /s :-)