原文:The Deno Handbook: A TypeScript Runtime Tutorial with Code Examples

What is Deno

Node.js替代品 , 服务端JavaScript生态系统 , 与Node.js相比在许多方面进行了改进.

Deno特性:

基于JavaScript的现代特性
可扩展的标准库
Deno使用Rust和TypeScript编写并因此在多方面受益良多 , 天然支持TypeScript , 自动编译TypeScript文件
支持ES Module
无需包管理[package manager]
支持await , 实现了top-level await
内置测试设施
尽可能兼容浏览器端 , 如提供了内置的fetch和全局对象window

Node.js API基于callback回调函数 , 无法优雅地利用promises and async/await.

而Deno全面支持TypeScript以及现代标准库(Deno可承载所有使用现代技术书写的代码 , 因此无需维护向后兼容) , 相信未来会流行起来.

与Node.js的异同

同

基于 chrome V8 Engine发展而来
使用JavaScript开发服务端

异

Node.js编写自C++ and JavaScript , Deno编写自Rust and TypeScript
Node.js提供官方的npm包管理器 , 而Deno无包管理器但却允许你直接从URLs导入任意ES Module
Deno在其所有的APIs及标准库中使用现代ECMAScript特性 , 而Node.js使用基于回调函数的标准库且无相关的升级计划
Deno通过权限[permissions]提供了安全层沙盒. 用户可以通过设置flags命令参数控制程序的访问权限 ; Node.js程序可以访问用户所能访问到的任意内容
- 沙盒可阻止程序做任何你不允许其做的事情 , 如是否允许程序访问本地系统的内容或使用网络与外界通信 , deno run --allow-net app.ts
从长远看 , Deno有将程序在无需外部依赖的前提下编译为可执行文件的预想可能性 , 类似Go, 该设想将带来革命性的影响 !

Deno 标准库

archive : tar archive utilities
async : async utilties
bytes : helpers to manipulate bytes slices
datetime : date/time parsing
encoding : encoding/decoding for various formats
flags : parse command-line flags
- --allow-env allow environment access
- --allow-hrtime allow high resolution time measurement
- --allow-net=<allow-net> allow network access
- --allow-plugin allow loading plugins
- --allow-read=<allow-read> allow file system read access
- --allow-run allow running subprocesses
- --allow-write=<allow-write> allow file system write access
- --allow-all allow all permissions (same as -A)
fmt : formatting and printing
fs : file system API
hash : crypto lib
http : HTTP server
io : I/O lib
log : logging utilities
mime : support for multipart data
node : Node.js compatibility layer
path : path manipulation
ws : websockets

基于 Deno 的框架

Demo : use Oak to build a REST API

Create `app.ts`

import { Application, Router } from "https://deno.land/x/oak/mod.ts";

const env = Deno.env.toObject();
const PORT = env.PORT || 4000;
const HOST = env.HOST || "127.0.0.1";

const router = new Router();
const app = new Application();

define an interface for a Dog

interface Dog {
  name: string;
  age: number;
}

let dogs: Array<Dog> = [
  {
    name: "Roger",
    age: 8,
  },
  {
    name: "Syd",
    age: 7,
  },
];

implement the API & add to Router

const router = new Router()

router
  .get('/dogs', getDogs)
  .get('/dogs/:name', getDog)
  .post('/dogs', addDog)
  .put('/dogs/:name', updateDog)
  .delete('/dogs/:name', removeDog)

const getDogs = ({ response }: { response: any }) => {
  response.body = dogs;
};

const getDog = ({
  params,
  response,
}: {
  params: {
    name: string;
  };
  response: any;
}) => {
  const dog = dogs.filter((dog) => dog.name === params.name);
  if (dog.length) {
    response.status = 200;
    response.body = dog[0];
    return;
  }

  response.status = 400;
  response.body = { msg: `Cannot find dog ${params.name}` };
};

const addDog = async ({
  request,
  response,
}: {
  request: any;
  response: any;
}) => {
  const body = await request.body();
  console.log(body, JSON.parse(body.value));

  const dog: Dog = body.value;
  dogs.push(dog);

  response.body = { msg: "OK" };
  response.status = 200;
};

const updateDog = async ({
  params,
  request,
  response,
}: {
  params: {
    name: string;
  };
  request: any;
  response: any;
}) => {
  const temp = dogs.filter((existingDog) => existingDog.name === params.name);
  const body = await request.body();
  const { age }: { age: number } = body.value;

  if (temp.length) {
    temp[0].age = age;
    response.status = 200;
    response.body = { msg: "OK" };
    return;
  }

  response.status = 400;
  response.body = { msg: `Cannot find dog ${params.name}` };
};

const removeDog = ({
  params,
  response,
}: {
  params: {
    name: string;
  };
  response: any;
}) => {
  const lengthBefore = dogs.length;
  dogs = dogs.filter((dog) => dog.name !== params.name);

  if (dogs.length === lengthBefore) {
    response.status = 400;
    response.body = { msg: `Cannot find dog ${params.name}` };
    return;
  }

  response.body = { msg: "OK" };
  response.status = 200;
};

run `app.ts`

deno run --allow-env --allow-net app.ts

[译]Deno 概览(附Demo)