# Deploying pyjs
## Prerequisites:
Before we start, let's introduce a few concepts and tools that are used in the pyjs workflow.
### Emscripten-forge
[Emscripten-forge](https://github.com/emscripten-forge/recipes) is similar to [conda-forge](https://conda-forge.org/) and provides packages compiled to webassembly using emscripten.
### Empack
https://github.com/emscripten-forge/empack is a tool to "pack" conda environments into a set of files that can be consumed by pyjs.
## Installation Steps
So we assume there is a directory called `/path/to/deploy` where we will
put all files which need to be served to the user.
### Define a conda environment
Pyjs has a conda-like workflow. This means the first step
is to create an environment with the `pyjs` package installed
and all packages required for the project.
```yaml
name: my-pyjs-env
channels:
- https://repo.prefix.dev/emscripten-forge/6x
- conda-forge
dependencies:
- pyjs-dev
- numpy
```
The name of the environment can be chosen by the user.
The `channels` section specifies the conda channels to use.
The emscripten-forge channel (`https://repo.prefix.dev/emscripten-forge/6x`)
is mandatory, it provides `pyjs` and all other packages compiled to WebAssembly.
The `conda-forge` channel is used for `noarch` (pure Python) packages.
`pyjs-dev` contains the pyjs Python module (`pyjs`) and the pyjs runtime
(`libpyjs-static`, with `lib_js/pyjs/pyjs_runtime_browser.{js,wasm}`).
### Create the environment
Assuming the yaml file above is called `environment.yml` and is in the current directory, the environment can be created using `micromamba`:
```Bash
micromamba create -f environment.yml --platform emscripten-wasm32 --prefix /path/to/env
```
### Copy pyjs
Copy the pyjs binary from the environment to the deploy directory.
This should move pyjs_runtime_browser.js and pyjs_runtime_browser.wasm to the deployment directory.
```Bash
cp /path/to/env/lib_js/pyjs/* /path/to/deploy
```
### Pack the environment
After the environment is defined, the next step is to pack the environment using `empack`.
```Bash
empack pack env --env-prefix /path/to/env --outdir /path/to/deploy
```
This will create a tarball for each package in the environment and a `empack_env_meta.json` file that describes the environment.
### The html/JavaScript code
The last step is to create a html file that loads the pyjs runtime and the packed environment.
```html
Pyjs Example
Pyjs Example
```