Deno

A secure runtime for JavaScript and TypeScript

Introduction & Comparison

Deno is a simple, modern and secure runtime for JavaScript and TypeScript that uses V8 and is built in Rust.

Difference with Node.js

• Node.js is written in C++; Deno is written in Rust

• Event-Loop: Node.js use libuv; Deno use Tokio library

• The dependency manager: Node.js use package.json and NPM

• Dependency folder: Deno use global cache folder(It defaults to the system's cache directory, also can be specified by DENO_DIR); Node.js use node_modules in every project

• import module: Deno support ES Moudule syntax, Node.js use requre() which is CommonJS syntax; Deno need to specify ext

• specific permissions, security

• GYP

• One delivrable, one executable: deno bundle, deno compile

• ecosystem

• Deno is compatible with Browser

• Deno provides built-in tooling like unit testing, code formatting, and linting to improve developer experience.

10 Things I Regret About Node.js

Benchmark

• 100 concurrent connections

|Name|version|AVG req/sec| |---|---|---|---| |node.http|12.16.3|47969.2| |deno.http|1.0.0|47376| |deno.http|1.1.0|46953.7| |node.http|14.2.0|44409|

• 10 concurrent connections

|Name|version|AVG req/sec| |---|---|---|--- |node.http|12.16.3|49926.69| |node.http|14.2.0|45345.33| |deno.http|1.1.0|34806.79| |deno.http|1.0.0|34742.37|

Setup

Install

# install
curl -fsSL https://deno.land/x/install/install.sh | sh
## or
brew install deno

# update
deno upgrade

Run

Access

Deno uses command-line options to explicitly allow access to different parts of the system

• environment access
• network access
• file system read/write access
• running a subprocess

Basic mode

deno run {local filepath}
# or
deno run {remote url}

Watch mode

like nodemon, will auto restart server if file changes in watching dirs

First, need to install denon, if occur error, try to update your deno and then try install again

deno install --unstable --allow-read --allow-run -f https://deno.land/x/denon/denon.ts

Then, touch a local configuration files for denon

{
  "files": [
    "./example/server.ts",
    "./example/static_server.ts"
  ],
  "quiet": false,
  "debug": true,
  "fullscreen": true,
  "extensions": [
    ".js",
    ".ts",
    ".py",
    ".json"
  ],
  "interval": 500,
  "watch": [
    "./"
  ],
  "deno_args": [
    "--allow-net",
    "--allow-read",
    "--import-map=import-map.json"
  ],
  "scripts": {
    "start_static": {
      "cmd": "./example/static_server.ts",
      "desc": "run static server"
    },
    "start": {
      "cmd": "./example/server.ts",
      "desc": "run server"
    },
    "test": {
      "cmd": "deno test",
      "desc": "exec test"
    }
  },
  "execute": {
    ".js": [
      "deno",
      "run"
    ],
    ".ts": [
      "deno",
      "run"
    ],
    ".py": [
      "python"
    ]
  },
  "allow": [
    "net",
    "read"
  ],
  "fmt": false,
  "unstable": true,
  "test": true
}

Finally, run in watching mode

denon -c {configuration file path}

Library

• Standard Library A standard set of high quality code, which are reviewed by the Deno core team

• Third Party Library

• Custom Local library

Import Module

• Import statements can make use of URLs

  # standard library
  https://deno.land/std/<PATH_TO_MODULE>.ts
  https://deno.land/std@{VERSION}/<PATH_TO_MODULE>.ts

• Import statements must have a file ending

Run Test

This will run all files in the working directory that end in _test or .test with the extension .js, .ts, .jsx, or .tsx

deno test

Conclusion

Deno successfully removes many of the drawbacks from Node.js development

Hope it's a better Node.js

It may not com replace Node.js

Reference

Deno 1.0: What you need to know

Deno, first approach

Deno 内部代码将停用 TypeScript，并公布五项具体理由

Performance aspect of Deno vs. Node