Deno vs Node.js：运行时之争

// Deno权限API
const status = await Deno.permissions.query({ name: "read", path: "/etc" });
console.log(status.state); // "granted" | "denied" | "prompt"

// 运行时请求权限
const result = await Deno.permissions.request({ name: "net", host: "api.example.com" });
if (result.state === "granted") {
    const resp = await fetch("https://api.example.com/data");
}

// Node.js: 需要额外配置
// 1. 安装typescript + ts-node/tsx
// 2. 配置tsconfig.json
// 3. 使用tsx运行或编译后运行

// 项目设置
// npm install -D typescript @types/node ts-node
// npx tsc --init

// 运行方式
// npx tsx src/app.ts
// 或 node --loader ts-node/esm src/app.ts

// ============================================

// Deno: 原生支持，零配置
// deno run app.ts

// Deno自带类型检查
// deno check app.ts

// 跳过类型检查（更快）
// deno run --no-check app.ts

// Deno示例 - 无需任何配置
interface User {
    id: number;
    name: string;
    email: string;
}

async function fetchUser(id: number): Promise<User> {
    const resp = await fetch(`https://jsonplaceholder.typicode.com/users/${id}`);
    return resp.json();
}

const user = await fetchUser(1);
console.log(`Hello, ${user.name}!`);

// 直接运行:
// deno run --allow-net app.ts

// Node.js模块导入
import express from 'express';                    // npm包
import { readFile } from 'fs/promises';           // 内置模块
import { myUtil } from './utils.js';              // 本地文件

// Deno模块导入 - 多种方式
// 1. URL导入（Deno原生方式）
import { serve } from "https://deno.land/[email protected]/http/server.ts";

// 2. npm:协议（兼容npm生态）
import express from "npm:express@4";
import chalk from "npm:chalk@5";

// 3. JSR (JavaScript Registry - Deno推荐)
import { join } from "jsr:@std/path@1";
import { parse } from "jsr:@std/csv@1";

// 4. Import Maps（配置别名）
// deno.json:
// {
//   "imports": {
//     "@std/": "jsr:@std/",
//     "express": "npm:express@4",
//     "~/": "./src/"
//   }
// }

// 使用别名导入
import { join } from "@std/path";
import express from "express";
import { config } from "~/config.ts";

// ===== 文件操作 =====

// Node.js
import { readFile, writeFile } from 'fs/promises';
const data = await readFile('file.txt', 'utf-8');
await writeFile('output.txt', data);

// Deno
const data = await Deno.readTextFile('file.txt');
await Deno.writeTextFile('output.txt', data);

// ===== HTTP服务器 =====

// Node.js
import { createServer } from 'http';
const server = createServer((req, res) => {
    res.writeHead(200);
    res.end('Hello');
});
server.listen(3000);

// Deno (内置Web标准API)
Deno.serve({ port: 3000 }, (req) => {
    return new Response('Hello');
});

// ===== HTTP请求 =====

// Node.js (需要node-fetch或内置fetch)
const resp = await fetch('https://api.example.com/data');
const json = await resp.json();

// Deno (fetch是全局内置的)
const resp = await fetch('https://api.example.com/data');
const json = await resp.json();

// ===== 测试 =====

// Node.js (内置test runner, Node 20+)
import { test, describe, it } from 'node:test';
import assert from 'node:assert';

describe('math', () => {
    it('should add', () => {
        assert.strictEqual(1 + 1, 2);
    });
});

// Deno (内置测试)
Deno.test('math - should add', () => {
    assertEquals(1 + 1, 2);
});

// Deno BDD风格
import { describe, it, expect } from "jsr:@std/testing/bdd";

describe('math', () => {
    it('should add', () => {
        expect(1 + 1).toBe(2);
    });
});

// Express (Node.js)
import express from 'express';
const app = express();

app.get('/api/users/:id', async (req, res) => {
    const user = await getUser(req.params.id);
    res.json(user);
});

app.listen(3000);

// ============================================

// Hono (Deno / Node.js / Bun / Workers)
import { Hono } from 'hono';
const app = new Hono();

app.get('/api/users/:id', async (c) => {
    const user = await getUser(c.req.param('id'));
    return c.json(user);
});

Deno.serve(app.fetch);

// ============================================

// Oak (Deno原生)
import { Application, Router } from "jsr:@oak/oak@16";

const router = new Router();
router.get('/api/users/:id', async (ctx) => {
    const user = await getUser(ctx.params.id);
    ctx.response.body = user;
});

const app = new Application();
app.use(router.routes());
await app.listen({ port: 3000 });

// Deno Deploy示例 - 部署到全球边缘
import { Hono } from "jsr:@hono/hono";

const app = new Hono();
const kv = await Deno.openKv(); // Deno KV - 全球分布式数据库

app.get("/api/visits", async (c) => {
    const key = ["visits", "total"];
    const result = await kv.get<number>(key);
    const count = (result.value ?? 0) + 1;
    await kv.set(key, count);
    return c.json({ visits: count });
});

app.get("/", (c) => {
    return c.html(`<h1>Hello from the Edge!</h1>`);
});

Deno.serve(app.fetch);

// Deno 2.0运行Node.js代码
// 大多数Node.js代码可以直接运行

// 使用Node.js内置模块
import { readFileSync } from "node:fs";
import { join } from "node:path";
import { createServer } from "node:http";

// 使用npm包
import chalk from "npm:chalk@5";
import lodash from "npm:lodash@4";

console.log(chalk.green("Hello from Deno with npm packages!"));

// 甚至可以使用package.json
// deno会自动读取package.json中的dependencies

// 从Node.js迁移到Deno的常见变化

// 1. 文件扩展名必须写全
// Node.js
import { helper } from './utils';        // 可以省略.js
// Deno
import { helper } from './utils.ts';     // 必须写.ts

// 2. 使用node:前缀访问Node API
// Node.js
import fs from 'fs';
// Deno
import fs from 'node:fs';

// 3. 全局对象差异
// Node.js
const buf = Buffer.from('hello');
// Deno (需要从node:buffer导入)
import { Buffer } from 'node:buffer';
const buf = Buffer.from('hello');

// 4. __dirname / __filename
// Node.js
console.log(__dirname);
console.log(__filename);
// Deno
console.log(import.meta.dirname);     // Deno 1.40+
console.log(import.meta.filename);

// 5. process对象
// Node.js
console.log(process.env.HOME);
// Deno
console.log(Deno.env.get('HOME'));
// 或兼容方式
import process from 'node:process';
console.log(process.env.HOME);