add Express Hello World example

fixes: #122

README.md

@@ -105,6 +105,7 @@ run ({ state, main })
 ### More Examples
 
 - [Star Wars Console](examples/star-wars-console) - Check this out!
+- [Express Hello World](examples/star-wars-console) - `express` Hello World.
 - [Async Simple](examples/async-simple)
 - [Hello World](examples/hello-world)
 - [Conditionals](examples/conditionals)

examples/express-hello-world/.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+  "editor.formatOnSave": false
+}

examples/express-hello-world/README.md

@@ -0,0 +1,36 @@
+# MojiScript Express Hello World
+
+App demonstrates how to interop with JavaScript libraries in a MojiScript application. In this case, we are interoping with `express` to create a simple web server that listens on port 3000.
+
+## Install
+
+```bash
+# clone repository
+git clone https://github.com/joelnet/MojiScript.git
+
+# enter directory
+cd MojiScript/examples/hello-world
+
+# install dependencies
+npm ci
+```
+
+## Run
+
+```bash
+npm start
+```
+
+You should see the output
+
+```
+Listening on port 3000.
+```
+
+## Code
+
+[index.mjs](index.mjs) - Load dependencies and settings and start the application.
+
+[main.mjs](main.mjs) - Entrypoint of application.
+
+[interop/express.mjs](interop/express.mjs) - `express` JavaScript iterop.

examples/express-hello-world/index.mjs

@@ -0,0 +1,15 @@
+import logF from 'mojiscript/console/logF'
+import run from 'mojiscript/core/run'
+import express from './interop/express'
+import main from './main'
+
+const dependencies = {
+  express: express (),
+  logF
+}
+
+const state = {
+  port: 3000
+}
+
+run ({ dependencies, state, main })

examples/express-hello-world/interop/express.mjs

@@ -0,0 +1,17 @@
+/**
+ * Interop file converts the JavaScript express library into a MojiScript compatible library.
+ */
+import express from 'express'
+
+export default () => {
+  // wrap app in our own function so we can return MojiScript compatible `get` and `listen`.
+  const app = express()
+
+  return {
+    // curry `get` and `handler
+    get: path => handler => app.get(path, (req, res) => handler(req)(res)),
+
+    // convert callback into a Promise.
+    listen: port => new Promise(resolve => app.listen(port, data => resolve(data)))
+  }
+}

examples/express-hello-world/main.mjs

@@ -0,0 +1,17 @@
+import pipe from 'mojiscript/core/pipe'
+import tap from 'mojiscript/function/tap'
+import $ from 'mojiscript/string/template'
+
+const defaultRoute = () => res => res.send ('Hello World')
+const startExpress = express => ({ port }) => express.listen (port)
+const setupRoutes = express => pipe ([
+  () => express.get ('/') (defaultRoute)
+])
+
+const main = ({ express, logF }) => pipe ([
+  tap (setupRoutes (express)),
+  tap (startExpress (express)),
+  logF ($`Listening on port ${'port'}.`)
+])
+
+export default main