Node.js: Where are we now, where are we going?

class: center, middle

# Node.js: Where are we now, where are we going?

---

# Who am I?

* Anna Henningsen
* addaleax on Twitter + Github
* she/her
* Active Node.js contributor since December 2015
* Node.js TSC

---

name: how-did-i

# How did I get into Node core?

```js
setTimeout(1000, 1000, function() { console.log('hi!'); });
```

---
template: how-did-i

(don’t ask me why)

```
> TypeError: callback.call is not a function
    at ontimeout [as _onTimeout] (timers.js:195:34)
    at Timer.listOnTimeout (timers.js:92:15)
```

---
template: how-did-i

```diff
@@ -177,6 +177,10 @@ exports.enroll = function(item, msecs) {

exports.setTimeout = function(callback, after) {
+  if (typeof callback !== 'function') {
+    throw new TypeError('"callback" argument must be a function');
+  }
+
   after *= 1; // coalesce to number or NaN

if (!(after >= 1 && after <= TIMEOUT_MAX)) {
```

---

# Why am I talking about this?

- I didn’t know much about what was happening inside Node.js
- A lot of people in the community don’t

--
- There’s a hidden world here

---

# Node 10 is near

Past & upcoming changes:

- ESM, HTTP/2, async_hooks, N-API
- Promises, URL, TextDecoder
- V8 6.6 / 6.7, WebAssembly, no more Debug API
- Error system changes
- Longer-term things, e.g. ChakraCore

Let’s go into more detail

---

# ES Modules

- Experimental, but available
- `.mjs`: Sorry, this is happening
  - But that doesn’t have to be the end of it
- `import.meta` is there
- Async loading
- It’s not going to work 100 % like Babel
- Names imports for CJS: Maybe not?

---

# ES Modules

```js
import fs from 'fs';                       // Works
import { readFile } from 'fs';             // Probably will work
import { foo } from './other-esm-module';  // Works

import.meta.url;                           // URL of the current file
import.meta.require;                       // Probably will work
```

---

# HTTP/2

- Experimental in Node 10, but probably not much longer
- Cleaner API than HTTP/1
- Compatibility API is available
- Multiplexing + push streams!

---

# HTTP/2

```js
const server = http2.createServer();

server.on('stream', (stream, headers) => {
  // stream is a Duplex
  stream.respond({
    'content-type': 'text/html',
    ':status': 200
  });
  stream.end('<h1>Hello World</h1>');
});

server.listen(8443);
```

---

# Diagnostics: async_hooks

- What is in the event loop?
- What is causing what: Tracking context
- Replaces `domain`s almost completely
- Native addon authors: Watch out!
- Still experimental, API has rough edges

---

# Diagnostics: async_hooks

```js
async_hooks.createHook({
  init(id, type, trigger) { process._rawDebug('init', id, type, trigger) },
  before(id) { process._rawDebug('before', id) },
  after(id) { process._rawDebug('after', id) },
  destroy(id) { process._rawDebug('destroy', id) }
}).enable();

fs.readFile(__filename, console.log);
```

---

# Diagnostics: async_hooks

```txt
init 6 FSREQWRAP 1
before 6
init 7 FSREQWRAP 6
after 6
destroy 6
before 7
init 8 FSREQWRAP 7
after 7
destroy 7
before 8
init 9 FSREQWRAP 8
…
```

---

# Diagnostics: perf_hooks

- Browser API ported to Node
- Support for Node-specific events
- Low-overhead timers
- Experimental

```js
performance.mark('A');
doSomeLongRunningProcess(() => {
  performance.mark('B');
  performance.measure('A to B', 'A', 'B');
  const measure = performance.getEntriesByName('A to B')[0];
  console.log(measure.duration);
});
```

---

# N-API

- Not experimental in Node 10 🎉
- Better everything
- ABI-stable, C or C++
- Much much (much) cleaner

```c++
Value AddFortyTwo(const CallbackInfo& info) {
  Value argument = info[0];
  int32_t result = argument.ToNumber().Int32Value() + 42;
  return Number::New(info.Env(), result);
}
```

---

# Promises

- `async/await` is … *really* nice.
- `await` support in the REPL
- `util.promisify`: Node 8+
- `fs/promises`: Coming in Node 10
- Async iterators: Coming!

---

# Errors

- `error.code` is being standardized in Node
- Error message changes: no longer semver-major

```js
> net.createServer().listen([1,2,3])
Error [ERR_INVALID_OPT_VALUE]: The value "[ 1, 2, 3 ]" is invalid for option "options"
    at Server.listen (net.js:1528:9)
> _err.code
'ERR_INVALID_OPT_VALUE'
```

---

# Workers

- Work in a fork
- Improve the embedder use case a lot as well
- Maybe soon?
- **Do you know somebody who is very familiar with the Windows C API? Help wanted!**

```js
const { Worker, isMainThread, postMessage } = require('worker');

if (isMainThread) {
  const worker = new Worker(__filename);
  worker.on('message', (message) => { ... });
  worker.on('exit', (code) => { ... });
} else {
  postMessage('Hi!');
}
```

---

# V8

- WebAssembly is there, and it’s fast
- Node 8+ has TurboFan + Ignition
  - There’s a whole new JS compiler pipeline 🎉
- `vm.runInDebugContext()` is no longer there
- Native module API: Pretty stable!
- Node is in V8’s CI
- For Node 10.0.0: V8 6.6 with ABI of 6.7
  - Possibly a few updates on top of that later

---

# ChakraCore

- Long-term effort
- Has own public releases, check them out!

# OpenSSL integration

- Would have liked to support 1.0.2, 1.1.0, 1.1.1 for Node 10?
- OpenSSL 1.0.2 is supported until end of 2019
- OpenSSL 1.1.1 comes with TLS v1.3 support

- (Honestly: I’m not sure where we’re standing at this point)

---

# ⚠ Reminder: No more `new Buffer()`!

- Buffer constructor is deprecated
- Check your code for vulnerabilities!
  - `new Buffer(string)` ← Is `string` always a string?
- Zero-fills now. Please don’t rely on that.
- Runtime deprecation: Coming in Node 10, outside `node_modules`

```js
const json = JSON.parse(request.body);
response.write(new Buffer(json.someString));
```

---

# Streams … streams?

- Complex, with noticeable overhead :(
- New low-level streams API might be coming
- Large re-work on the C++ side
- Goal: C++-only fast path for `.pipe()`

---

# Finally: So long, Node 4

- Node 4 is supported until April 2018
- Node 6 is supported until **April 2019**
- Node 8 is supported until **December 2019**
- Node 9 is supported until June 2018
- Node 10 is coming out next week!

---

# That’s it!

- Thank you for listening!
- If you have questions, feel free to talk to me / ping me
- If you have a Node.js wishlist, feel free to talk to me / ping me
- Node.js is Open Source. You can contribute!

Slides @ https://addaleax.net/talk-berlinjs/