Vue: Private properties prefixed with `$_` (dollar underscore) are not available inside component

[adriangoransson]

Version

2.5.16

Reproduction link

https://jsfiddle.net/jfyLx256/

Steps to reproduce

Prefix a property with $_ and try to reference it within the component or template.

What is expected?

$_ prefixed properties should be rendered in template and available within the component.

What is actually happening?

$_ props are undefined. Not rendered in template and undefined in component logic.

---

Private property names are described in the Vue style guide and the $_ form is officially recommended. https://vuejs.org/v2/style-guide/#Private-property-names-essential.

I first noticed this in a project built with [email protected].

[posva]

This is expected: https://vuejs.org/v2/api/#data, You can access them with $data.$_foo

[posva]

@chrisvfritz do you think we should add a note about them not being proxied in the style guide?

[adriangoransson]

I definitely think this should be mentioned in the style guide. I've been using Vue for about six months now and until now didn't know about $data because I never needed to.

I can't recall any place in the documentation where it's actually used either, so I'd wager most people have forgot about it if they ever read it.

Edit: Thanks for the quick help though! Much appreciated :)

[adriangoransson]

Actually... Since these property names are recommended and at least according to the style guide guaranteed to not conflict with Vue, doesn't it make more sense to just proxy them?

[posva]

We had a discussion about this in a PR. Unfortunately, I don't remember which PR it was nor I remember the final outcome 😆

[trafium]

Encountered this behaviour because I just started to follow style guide more thoroughly. So now I seemingly should fill my mixins' methods/computed/hooks with messy stuff like this.$data.$_mixinName_itemName everywhere, which, in my opinion, unnecessarily hurts readability since, as @adriangoransson said, conflicts are not expected in this situation.

[VitorLuizC]

Where I can find this on docs? I've taken more than an hour just searching why my data property doesn't work... Would be better to just support dollar prefixed properties.

[Justineo]

@VitorLuizC

https://vuejs.org/v2/api/#data