Intro to Node.js

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# Intro to Node.js

The V8 non-blocking asynchronous JavaScript runtime.

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# Intro to Node.js

The ....... Whaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa?

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# What is Node.js?

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# What is Node.js?

**A set of non-blocking IO bindings for the V8 JavaScript VM:**

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# What is Node.js?

**~~A set of non-blocking~~ IO bindings for ~~the~~ V8 ~~JavaScript VM~~:**

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# What is Node.js?

**                                           IO bindings for        V8                            :**

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# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8**

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# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8** - Google Chrome's JavaScript *Virtual Machine*

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# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8** - Google Chrome's JavaScript *Virtual Machine*
- **Node.js**

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# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8** - Google Chrome's JavaScript *Virtual Machine*
- **Node.js** - IO bindings for V8:

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# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8** - Google Chrome's JavaScript *Virtual Machine*
- **Node.js** - IO bindings for V8:
  - filesystem

---

# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8** - Google Chrome's JavaScript *Virtual Machine*
- **Node.js** - IO bindings for V8:
  - filesystem
  - networking

---

# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8** - Google Chrome's JavaScript *Virtual Machine*
- **Node.js** - IO bindings for V8:
  - filesystem
  - networking
  - stdin/stdout/stderr

---

# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8** - Google Chrome's JavaScript *Virtual Machine*
- **Node.js** - IO bindings for V8:
  - filesystem
  - networking
  - stdin/stdout/stderr
  - database access

---

# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8** - Google Chrome's JavaScript *Virtual Machine*
- **Node.js** - IO bindings for V8:
  - filesystem
  - networking
  - stdin/stdout/stderr
  - database access
- **They're asynchronous!**

---

# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8** - Google Chrome's JavaScript *Virtual Machine*
- **Node.js** - IO bindings for V8:
  - filesystem
  - networking
  - stdin/stdout/stderr
  - database access
- **They're asynchronous!** - IO runs in parallel by default

---

# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8** - Google Chrome's JavaScript *Virtual Machine*
- **Node.js** - IO bindings for V8:
  - filesystem
  - networking
  - stdin/stdout/stderr
  - database access
- **They're asynchronous!** - IO runs in parallel by default
- **They're fast!**

---

# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8** - Google Chrome's JavaScript *Virtual Machine*
- **Node.js** - IO bindings for V8:
  - filesystem
  - networking
  - stdin/stdout/stderr
  - database access
- **They're asynchronous!** - IO runs in parallel by default
- **They're fast!** - V8 & Node.js   are written in C/C++

---

# What is Node.js?

**                                           IO bindings for        V8                            :**

- **V8** - Google Chrome's JavaScript *Virtual Machine*
- **Node.js** - IO bindings for V8:
  - filesystem
  - networking
  - stdin/stdout/stderr
  - database access
- **They're asynchronous!** - IO runs in parallel by default
- **They're fast!** - V8 & Node.js* are written in C/C++

\* *mostly*

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# Demo: Hello World

```bash
# REPL
$ node
> console.log('Hello world')
Hello World

.
```

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# Demo: Hello World

```bash
# REPL
$ node
> console.log('Hello world')
Hello World

# File
$ echo "console.log('Hello world')" > foo.js
$ node foo.js
Hello World

.
```

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# Demo: Hello World

```bash
# REPL
$ node
> console.log('Hello world')
Hello World

# File
$ echo "console.log('Hello world')" > foo.js
$ node foo.js
Hello World

# Eval
$ node -e "console.log('Hello world')"
Hello World
```

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# Why Node.js?

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# Why Node.js?

**How is node.js different?**

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# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  <br>
  <br>
  <br>
  <br>
1. **JavaScript:**

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  <br>
  <br>
  <br>
  <br>
1. **JavaScript:**
  <br>
  <br>
  <br>
  <br>
1. ***Single-threaded* Event-loop:**

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  - All IO calls are backgrounded
  <br>
  <br>
  <br>
1. **JavaScript:**
  <br>
  <br>
  <br>
  <br>
1. ***Single-threaded* Event-loop:**

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  - All IO calls are backgrounded
  - Execution resumes when IO completes
  <br>
  <br>
1. **JavaScript:**
  <br>
  <br>
  <br>
  <br>
1. ***Single-threaded* Event-loop:**

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  - All IO calls are backgrounded
  - Execution resumes when IO completes
  - No legacy blocking APIs (No IO in V8)
1. **JavaScript:**
  <br>
  <br>
  <br>
  <br>
1. ***Single-threaded* Event-loop:**

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  - All IO calls are backgrounded
  - Execution resumes when IO completes
  - No legacy blocking APIs (No IO in V8)
1. **JavaScript:**
  - Unifies the front-end & mid-tier
  <br>
  <br>
  <br>
1. ***Single-threaded* Event-loop:**

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  - All IO calls are backgrounded
  - Execution resumes when IO completes
  - No legacy blocking APIs (No IO in V8)
1. **JavaScript:**
  - Unifies the front-end & mid-tier
  - Universal JavaScript
  <br>
  <br>
1. ***Single-threaded* Event-loop:**

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  - All IO calls are backgrounded
  - Execution resumes when IO completes
  - No legacy blocking APIs (No IO in V8)
1. **JavaScript:**
  - Unifies the front-end & mid-tier
  - Universal JavaScript - Share client/server code
  <br>
  <br>
1. ***Single-threaded* Event-loop:**

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  - All IO calls are backgrounded
  - Execution resumes when IO completes
  - No legacy blocking APIs (No IO in V8)
1. **JavaScript:**
  - Unifies the front-end & mid-tier
  - Universal JavaScript - Share client/server code
  - Server-side Rendering
1. ***Single-threaded* Event-loop:**

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  - All IO calls are backgrounded
  - Execution resumes when IO completes
  - No legacy blocking APIs (No IO in V8)
1. **JavaScript:**
  - Unifies the front-end & mid-tier
  - Universal JavaScript - Share client/server code
  - Server-side Rendering
1. ***Single-threaded* Event-loop:**
  - NGINX

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  - All IO calls are backgrounded
  - Execution resumes when IO completes
  - No legacy blocking APIs (No IO in V8)
1. **JavaScript:**
  - Unifies the front-end & mid-tier
  - Universal JavaScript - Share client/server code
  - Server-side Rendering
1. ***Single-threaded* Event-loop:**
  - NGINX
  - Netty or Reactor (Java)

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  - All IO calls are backgrounded
  - Execution resumes when IO completes
  - No legacy blocking APIs (No IO in V8)
1. **JavaScript:**
  - Unifies the front-end & mid-tier
  - Universal JavaScript - Share client/server code
  - Server-side Rendering
1. ***Single-threaded* Event-loop:**
  - NGINX
  - Netty or Reactor (Java)
  - Twisted or Tornado (Python)

---

# Why Node.js?

**How is node.js different?**

1. **Asynchronous non-blocking IO:**
  - All IO calls are backgrounded
  - Execution resumes when IO completes
  - No legacy blocking APIs (No IO in V8)
1. **JavaScript:**
  - Unifies the front-end & mid-tier
  - Universal JavaScript - Share client/server code
  - Server-side Rendering
1. ***Single-threaded* Event-loop:**
  - NGINX
  - Netty or Reactor (Java)
  - Twisted or Tornado (Python)
  - EventMachine (Ruby)

---

# Blocking vs Non-Blocking

**Blocking Code:**

```html
Read file from Filesystem
Print data
Do something unrelated
```

**Non-Blocking Code:**

```html
Read file from Filesystem
    // This is asynchronous
    On completion, Print data
Do something unrelated
```

---

# Blocking vs Non-Blocking

**Blocking Code:**

```js

Read file from Filesystem
Print data
Do something unrelated
```

**Non-Blocking Code:**

```js

Read file from Filesystem
    // This is asynchronous
    On completion, Print data

Do something unrelated
```

---

# Blocking vs Non-Blocking

**Blocking Code:**

```js

Read file from Filesystem
console.log(data)
doSomethingUnrelated()
```

**Non-Blocking Code:**

```js

Read file from Filesystem
    // This is asynchronous
    console.log(data)

doSomethingUnrelated()
```

---

# Blocking vs Non-Blocking

**Blocking Code:**

```js

let data = // Read file from Filesystem
console.log(data)
doSomethingUnrelated()
```

**Non-Blocking Code:**

```js

let data = // Read file from Filesystem
    // This is asynchronous
    console.log(data)

doSomethingUnrelated()
```

---

# Blocking vs Non-Blocking

**Blocking Code:**

```js

let data = fs.readFile    ('~/.bashrc')
console.log(data)
doSomethingUnrelated()
```

**Non-Blocking Code:**

```js

let data =       fs.readFile('~/.bashrc')
    // This is asynchronous
    console.log(data)

doSomethingUnrelated()
```

---

# Blocking vs Non-Blocking

**Blocking Code:**

```js

let data = fs.readFileSync('~/.bashrc')
console.log(data)
doSomethingUnrelated()
```

**Non-Blocking Code:**

```js

let data = await fs.readFile('~/.bashrc')
    // This is asynchronous
    console.log(data)

doSomethingUnrelated()
```

---

# Blocking vs Non-Blocking

**Blocking Code:**

```js

let data = fs.readFileSync('~/.bashrc')
console.log(data)
doSomethingUnrelated()
```

**Non-Blocking Code:**

```js

let data = await fs.readFile('~/.bashrc')
    // This is asynchronous
    console.log(data)

doSomethingUnrelated()
```

---

# Blocking vs Non-Blocking

**Blocking Code:**

```js

let data = fs.readFileSync('~/.bashrc')
console.log(data)
doSomethingUnrelated()
```

**Non-Blocking Code:**

```js

async function readFile() {
    let data = await fs.readFile('~/.bashrc')
    console.log(data)
}
readFile()
doSomethingUnrelated()
```

---

# Blocking vs Non-Blocking

**Blocking Code:**

```js
// BAD
let data = fs.readFileSync('~/.bashrc')
console.log(data)
doSomethingUnrelated()
```

**Non-Blocking Code:**

```js
// GOOD
async function readFile() {
    let data = await fs.readFile('~/.bashrc')
    console.log(data)
}
readFile()
doSomethingUnrelated()
```

---

# In Summary:    Blocking

```js
      function readFileSync() {
  let data =       fs.readFileSync('~/.bashrc')
  console.log(data)
}
readFileSync()
doSomethingUnrelated()
```

---

# In Summary: Non-Blocking

```js
async function readFile    () {
  let data = await fs.readFile    ('~/.bashrc')
  console.log(data)
}
readFile    ()
doSomethingUnrelated()
```

---

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### Always remember...

# **`async` & `await`**

<br/>

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### Always remember...

# **`async` & `await`**

*or else...*

---

# Blocking vs Non-Blocking

```javascript
async function readFile(filePath) {
  // Use await for serial execution
  let data = await fs.readFile(filePath)
  console.log(data)
}
readFile('~/.bashrc')
readFile('~/.bash_profile')
```

[![](./images/blocking_vs_nonblocking.png)](./images/blocking_vs_nonblocking.png)

---

# Parallel vs Serial

```javascript
async function swapFiles(filePathA, filePathB) {
  // Execute reads in parallel
  let [dataA, dataB] = await Promise.all([
    fs.readFile(filePathA),
    fs.readFile(filePathB)
  ])

// Execute writes in serial
  await fs.writeFile(filePathA, dataB)
  await fs.writeFile(filePathB, dataA)
}
```

[![](./images/blocking_vs_nonblocking.png)](./images/blocking_vs_nonblocking.png)

---

# When Node.js?

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# When Node.js?

**When should I use node.js:**

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# When Node.js?

**When should I use node.js:**

- IO-bound applications

---

# When Node.js?

**When should I use node.js:**

- ~~IO-bound applications~~

---

# When Node.js?

**When should I use node.js:**

- High-concurrency (many simultaneous IO requests)

---

# When Node.js?

**When should I use node.js:**

- High-concurrency (many simultaneous IO requests)
- Low-latency

---

# When Node.js?

**When should I use node.js:**

- High-concurrency (many simultaneous IO requests)
- Low-latency
- Unified JavaScript "front-end"

---

# When Node.js?

**When should I use node.js:**

- High-concurrency (many simultaneous IO requests)
- Low-latency
- Unified JavaScript "front-end" = mid-tier + client

---

# When Node.js?

**When should I use node.js:**

- High-concurrency (many simultaneous IO requests)
- Low-latency
- Unified JavaScript "front-end" = mid-tier + client*

<br>
\* Also, iOS & Android with React Native

---

# When Node.js?

**When should I use node.js:**

- High-concurrency (many simultaneous IO requests)
- Low-latency
- Unified JavaScript "front-end" = mid-tier + client*
- DevOps, tooling & other scripting environments

\* Also, iOS & Android with React Native

---

# Where Node.js

---

# Where Node.js

**What should you build?**

---

# Where Node.js

**What should you build?**

Anything that's         **IO**-bound:

---

# Where Node.js

**What should you build?**

Anything that's         **~~IO~~**-bound:

---

# Where Node.js

**What should you build?**

Anything that's **NOT CPU**-bound:

---

# Where Node.js

**What should you build?**

Anything that's **NOT CPU**-bound:

- Realtime Apps - *Websockets, Chat*

---

# Where Node.js

**What should you build?**

Anything that's **NOT CPU**-bound:

- Realtime Apps - *Websockets, Chat*
- Fast File Upload Server - *Especially large files*

---

# Where Node.js

**What should you build?**

Anything that's **NOT CPU**-bound:

- Realtime Apps - *Websockets, Chat*
- Fast File Upload Server - *Especially large files*
- Ad/Metrics Server

---

# Where Node.js

**What should you build?**

Anything that's **NOT CPU**-bound:

- Realtime Apps - *Websockets, Chat*
- Fast File Upload Server - *Especially large files*
- Ad/Metrics Server
- Tooling CLIs - *DevOps, CI, CD, QA*

---

# Where Node.js

**What should you build?**

Anything that's **NOT CPU**-bound:

- Realtime Apps - *Websockets, Chat*
- Fast File Upload Server - *Especially large files*
- Ad/Metrics Server
- Tooling CLIs - *DevOps, CI, CD, QA*
- API Server - *Mobile back-end*

---

# Where Node.js

**What should you build?**

Anything that's **NOT CPU**-bound:

- Realtime Apps - *Websockets, Chat*
- Fast File Upload Server - *Especially large files*
- Ad/Metrics Server
- Tooling CLIs - *DevOps, CI, CD, QA*
- API Server - *Mobile back-end*
- Unified "Front-end" - *Any Web Application!*

---

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# Questions?