What are the main differences between Deno and Node.js? - 面试题

Deno and Node.js are two popular JavaScript/TypeScript runtime environments, each with its own characteristics and use cases. Understanding their differences helps developers choose the right tool.

Historical Background

Node.js

Creator: Ryan Dahl
Release date: 2009
Goal: Enable JavaScript to run on the server side
Architecture: C++ + V8 JavaScript engine

Deno

Creator: Ryan Dahl (creator of Node.js)
Release date: 2020
Goal: Address Node.js design flaws and provide a more modern solution
Architecture: Rust + V8 JavaScript engine + Tokio event loop

Core Differences

1. Module System

Node.js

javascript
// CommonJS
const fs = require('fs');
const express = require('express');

// ES Modules
import fs from 'fs';
import express from 'express';

Deno

typescript
// Only supports ES Modules, imports via URL
import { serve } from "https://deno.land/std@0.208.0/http/server.ts";
import { Application } from "https://deno.land/x/oak@v12.6.1/mod.ts";

Differences:

Node.js supports both CommonJS and ES Modules
Deno only supports ES Modules
Deno uses URL for direct module imports, no package.json needed

2. Package Management

Node.js

json
// package.json
{
  "dependencies": {
    "express": "^4.18.2",
    "lodash": "^4.17.21"
  }
}

bash
npm install
npm install express --save

Deno

typescript
// Import directly from URL
import { serve } from "https://deno.land/std@0.208.0/http/server.ts";

bash
# No installation needed, run directly
deno run app.ts

# Cache dependencies
deno cache app.ts

Differences:

Node.js uses npm/yarn/pnpm and package.json
Deno doesn't need a package manager, imports directly from URL
Deno automatically caches downloaded modules

3. Security

Node.js

bash
# No security restrictions by default
node app.js

javascript
// Can freely access file system, network, etc.
const fs = require('fs');
fs.readFileSync('/etc/passwd'); // No restrictions

Deno

bash
# Secure by default, explicit authorization needed
deno run app.ts  # No permissions

deno run --allow-read app.ts  # Allow read
deno run --allow-net app.ts  # Allow network access
deno run --allow-all app.ts  # Allow all permissions (not recommended)

typescript
// Need permissions to access
const content = await Deno.readTextFile("/etc/passwd"); // Requires --allow-read

Differences:

Node.js has no security restrictions by default
Deno is secure by default, requires explicit authorization
Deno provides fine-grained permission control

4. TypeScript Support

Node.js

bash
# Need to install TypeScript
npm install -D typescript @types/node

# Need to configure tsconfig.json
tsc app.ts
node app.js

json
// tsconfig.json
{
  "compilerOptions": {
    "target": "ES2020",
    "module": "commonjs",
    "strict": true
  }
}

Deno

bash
# Native support, no configuration needed
deno run app.ts

typescript
// Run TypeScript directly
interface User {
  id: number;
  name: string;
}

const user: User = { id: 1, name: "John" };
console.log(user);

Differences:

Node.js needs TypeScript compiler and type definitions installed
Deno natively supports TypeScript, no extra configuration
Deno performs type checking at runtime

5. API Design

Node.js

javascript
// Callback style
fs.readFile('file.txt', (err, data) => {
  if (err) throw err;
  console.log(data);
});

// Promise style
fs.promises.readFile('file.txt')
  .then(data => console.log(data))
  .catch(err => console.error(err));

Deno

typescript
// Unified use of Promise
const data = await Deno.readTextFile('file.txt');
console.log(data);

Differences:

Node.js mixes callbacks and Promises
Deno uses Promises and async/await uniformly
Deno API is more modern

6. Standard Library

Node.js

javascript
// Built-in modules
const fs = require('fs');
const http = require('http');
const path = require('path');

Deno

typescript
// Import standard library from URL
import { serve } from "https://deno.land/std@0.208.0/http/server.ts";
import { ensureDir } from "https://deno.land/std@0.208.0/fs/mod.ts";
import { join } from "https://deno.land/std@0.208.0/path/mod.ts";

Differences:

Node.js modules are built into the runtime
Deno standard library is hosted on the web
Deno standard library updates more frequently

7. Toolchain

Node.js

bash
# Need to install various tools
npm install -D prettier eslint jest webpack
npx prettier --write .
npx eslint .
npm test

Deno

bash
# Built-in tools
deno fmt .           # Format
deno lint .          # Lint
deno test .          # Test
deno compile app.ts # Compile

Differences:

Node.js needs multiple external tools installed
Deno has all necessary tools built-in
Deno toolchain is more unified

8. Global Objects

Node.js

javascript
// Global objects
global
process
Buffer
__dirname
__filename
require
module
exports

Deno

typescript
// Global objects
Deno
window (browser compatible)
fetch (Web standard)
URL (Web standard)
URLSearchParams (Web standard)

Differences:

Node.js has unique global objects
Deno is closer to Web standards
Deno removed CommonJS-related objects like require/module

9. File Extensions

Node.js

javascript
// .js files
// .ts files need compilation

Deno

typescript
// .ts files
// .js files
// .mts files
// .mjs files

Differences:

Node.js mainly uses .js
Deno recommends .ts, but also supports other extensions

10. Configuration Files

Node.js

json
// package.json
{
  "name": "my-app",
  "version": "1.0.0",
  "dependencies": {},
  "devDependencies": {},
  "scripts": {}
}

// tsconfig.json
{
  "compilerOptions": {}
}

Deno

json
// deno.json
{
  "compilerOptions": {
    "strict": true
  },
  "tasks": {
    "dev": "deno run --watch app.ts",
    "test": "deno test"
  },
  "imports": {
    "std/": "https://deno.land/std@0.208.0/"
  }
}

Differences:

Node.js needs package.json and tsconfig.json
Deno only needs one deno.json file
Deno configuration is simpler

Performance Comparison

Startup Time

Node.js: Faster, C++ implementation
Deno: Slightly slower, but gap is narrowing

Runtime Performance

Node.js: Mature optimization, stable performance
Deno: Uses Rust and Tokio, faster in some scenarios

Memory Usage

Node.js: Lower memory footprint
Deno: Slightly higher memory usage, but still optimizing

Ecosystem Comparison

Package Count

Node.js: Over 2 million packages on npm
Deno: Thousands of packages on deno.land/x, growing rapidly

Community Size

Node.js: Huge community, rich resources
Deno: Fast-growing community, active development

Learning Resources

Node.js: Abundant tutorials, documentation, videos
Deno: Comprehensive documentation, increasing tutorials

Use Cases

Choose Node.js

Need to use many npm packages
Existing projects based on Node.js
Team familiar with Node.js ecosystem
Need mature ecosystem
Enterprise applications, high stability requirements

Choose Deno

New projects, pursuing modern development experience
Need better security
TypeScript first
Need built-in toolchain
Microservices architecture
Rapid prototyping

Migration Considerations

Migrating from Node.js to Deno

Rewrite module imports (require → import)
Remove package.json, use URL imports
Update API calls (Node.js API → Deno API)
Configure permission flags
Update test framework

Migrating from Deno to Node.js

Install dependencies (npm install)
Configure TypeScript
Rewrite module imports (URL → npm packages)
Update API calls (Deno API → Node.js API)
Remove permission-related code

Summary

Deno and Node.js each have their advantages:

Node.js: Mature and stable, rich ecosystem, suitable for large projects
Deno: Modern and secure, great development experience, suitable for new projects

The choice depends on project requirements, team skills, and long-term planning. Both are continuously evolving, and there may be more integration and borrowing in the future.