Underscore prefixes for "private" properties

[taion]

From the main section:

Use a leading underscore _ when naming private properties.

From the React section:

Do not use underscore prefix for internal methods of a React component.

These two seem a bit inconsistent.

[goatslacker]

A bit. The thing about React components is that all methods should be private so we just save ourselves the typing and don't insert the leading underscore.

[taion]

What do you mean? If I have e.g. a ref to an element, I can call methods on it just fine. I've seen this used to implement e.g. getValue methods on things like complex, uncontrolled input components for forms.

If you consider this an anti-pattern, it could be useful to add a clarifying comment to say to not do this. There are definitely problems with this pattern - it's not container-safe, for one.

[afilp]

I am also interested in an explanation to that. Not all methods are "internal" if we consider that we may call a component's method from the parent.

Example:

parent.jsx

    _handleOpenChildDialog() {
        this.refs.childComponent.showDialog();
    }

childComponent.jsx

    showDialog() {
        this.refs.myDialog.show();
    }

So, what is our general take on this? Do we still write all methods without any underscore?

[taion]

👍 Facebook, for example, use this pattern extensively: https://github.com/facebook/relay/blob/v0.4.0/src/container/RelayRootContainer.js

[hbrls]

@taion what about v0.14

[taion]

What about it?

[ljharb]

Personally, I think this pattern is horrifically bad. Things that are not private are not private - sticking an underscore in front of them doesn't make them private, it just lulls you into the false belief that you can make a breaking change without bumping a major version.

It's not private if it's accessible in the runtime. If it's private - ie, via closure or WeakMap - no convention or unit tests are needed. If it's not, it's public, and you must test it, and whether you document it or not, it is public and breaking it counts as a breaking change. At that point, using a leading underscore is just fluff, so why would you need a convention for it?

[taion]

@ljharb

That's totally fine - I personally don't mind writing my code either way (as long as I can point to a style guide and say that I'm following it).

The issue is that this style guide appears to be inconsistent between https://github.com/airbnb/javascript#22.4 and https://github.com/airbnb/javascript/tree/master/react#methods. I don't see how it's possible to follow both.

[ljharb]

React is a special subset - you could follow both by using _-prefixes in non-React code. I don't see a logical disconnect there.

[taion]

Okay. If that's intentional, I can live with it.

[ljharb]

JS doesn't have privacy. Underscore-prefixed things are just as public as anything else.

[goatslacker]

We should probably just remove this section from the main style guide or rephrase it. Same with the React style guide. This whole attachment to "private" is what makes the rules seem confusing.