docbrown/docs/frontend/webpacker.md
Nick Taylor ccf7e6e5bf
Upgrade to webpacker/webpack 4 and Babel 7 (#6664)
Upgraded to webpacker 4/webpack 4 and Babel 7
2020-03-17 08:20:36 -04:00

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---
title: Webpacker
---
# Webpacker
DEV has two Javascript codebases.
One contains plain Javascript, you can read about it
[in its own guide](/frontend/plain-js).
The other one is managed by [Webpacker](https://github.com/rails/webpacker), and
it's located inside `/app/javascripts`, written using ES6+.
Currently, it's mainly used for Preact components, served via `webpack` which is
integrated into the Rails app using `Webpacker`.
There is a packs directory `/app/javascript/packs` where you can create new
"pack" files. Pack files are initializers for Webpacker.
Since DEV is not a Single Page Application (SPA), Preact components are mounted
as needed by including the pack file in the view files.
For example:
```erb
<%= javascript_packs_with_chunks_tag "webShare", defer: true %>
```
The include statement corresponds to the pack
`app/javascripts/packs/webShare.js`
If you have more than one webpacker pack on the page, you need to include it in
the same `javascript_packs_with_chunks_tag` call. The reason being is it avoids
loading split chunks multiple times.
```erb
<%= javascript_packs_with_chunks_tag "webShare", "someOtherPack", defer: true %>
```
For more information in regards to `javascript_packs_with_chunks_tag`, see
https://github.com/rails/webpacker/blob/master/lib/webpacker/helper.rb