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Working with Node.js / npm in Code App

Node.js is a platform for building fast and scalable server applications using JavaScript. Node.js is the runtime and npm is the Package Manager for Node.js modules.

With release 1.2.0 (March 2021), Node.js (12.19.0) runtime comes preinstalled in Code App with npm support.

Running your first Node.js application

Let's start with creating a program that outputs a message to the console.

Create a file named index.js. You can either do it by the GUI or by a terminal command.

touch index.js

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Create a string variable and output it to the console with the following code

var msg = "Hello World";
console.log(msg);

Note that Code App will provide code suggestion (aka Intellisense) for Javascript based on your code's content. image

Now, you can save the file by pressing ⌘S. If you do not have a hardware keyboard, simply hide the keyboard by tapping the hide keyboard button at the bottom right corner.

image

Note that the circle icon became a cross icon. This indicates that the file is saved to the disk.

image

Running index.js

There are two ways you can run a program in Code App - remotely or locally. For Javascript, both ways are supported. You can run Node.js from the built-in terminal.

Open the terminal panel by pressing ⌘J, or the chevron (</>) icon on the sidebar and type node index.js. You should see the output of your script.

image

Creating an Express application

Express is a popular web application framework for building web apps and APIs. You can install it with the package manager npm.

Install Express with the following command:

npm install express

You should be able to see 2 newly created files and a directory called node_modules. node_modules is where npm store your installed modules.

image

Create a new file called index.js and type the followings:

const express = require('express')
const app = express()
const port = 3000

app.get('/', (req, res) => {
  res.send('Hello World!')
})

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`)
})

Start the server by the follwing command:

node index.js

A express server instance is now running at localhost:3000. You can verify this by launching Safari side by side and navigate to the url.

image

To stop the server, you can press control+c on the terminal or press the stop button.

Install Node.js modules globally

You can install extra terminal commands by installing Node.js modules globally. Examples include typescript and prettier.

To install a module globally, use the following command:

npm install {your_module_name} -g

You can now call the cli commands included in the package from anywhere. For example, tsc comes with typescript module. It transpiles TypeScript code into Javascript.

Limitations

Due to iOS restrictions, limitations apply when running Node.js or npm in Code App. Most noticibly:

  • Depending on your device model, memory available to your Node.js runtime could be quite limited. For example, it's around 180MB on iPad 8th generation. This means large modules or npm installation with large amount of dependencies might fail.
  • Modules with native code will not run. You will likely be prompted with EPERM errors.
  • Code that spawn process will not run. For example, child_process will never work.
  • Node.js will not run in the background (when the app is dismissed).