全球简讯:Node.js 19正式发布,聊聊它的 6 大特性!

时间:2022-11-16 20:48:07       来源:转载
Node 19已正式发布,下面本篇文章就来带大家详解了解一下Node.js 19的 6 大特性,希望对大家有所帮助!


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Node.js 14 将在 2023 年 4 月结束更新维护,Node.js 16 (LTS) 预计将在 2023 年 9 月结束更新维护。

而Node 19 在 2022-10-18 发布。【相关教程推荐:nodejs视频教程】

我们知道 Node.js 版本分两种:LTS 和 Current

其中,Current 版本通常每 6 个月发布一次。

每年 4 月份发布新的偶数版本;

每年 10 月份发布新的奇数版本;

在刚过去的 10 月,发布的 V19.0.1 成为最新的 “Current” 尝鲜版,它一共带来 6 大特性。

1. HTTP(S)/1.1 KeepAlive 默认为 true

Node.js v19 设置 keepAlive 默认值为 true,这意味着所有出站的 HTTP(s) 连接都将使用 HTTP 1.1 keepAlive,默认时间为 5S;

代码测试:

const http = require("node:http");console.log(http.globalAgent);const https = require("node:https");console.log(https.globalAgent);
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我们可以对比看看 v16 和 v19 的 node server Agent 配置差异:

V16
% nvm use 16Now using node v16.0.0 (npm v7.10.0)% node serverAgent {  _events: [Object: null prototype] {    free: [Function (anonymous)],    newListener: [Function: maybeEnableKeylog]  },  _eventsCount: 2,  _maxListeners: undefined,  defaultPort: 80,  protocol: "http:",  options: [Object: null prototype] { path: null },  requests: [Object: null prototype] {},  sockets: [Object: null prototype] {},  freeSockets: [Object: null prototype] {},  keepAliveMsecs: 1000,  keepAlive : false,  maxSockets: Infinity,  maxFreeSockets: 256,  scheduling: "lifo",  maxTotalSockets: Infinity,  totalSocketCount: 0,  [Symbol(kCapture)]: false}Agent {  _events: [Object: null prototype] {    free: [Function (anonymous)],    newListener: [Function: maybeEnableKeylog]  },  _eventsCount: 2,  _maxListeners: undefined,  defaultPort: 443,  protocol: "https:",  options: [Object: null prototype] { path: null },  requests: [Object: null prototype] {},  sockets: [Object: null prototype] {},  freeSockets: [Object: null prototype] {},  keepAliveMsecs: 1000,  keepAlive: false,  maxSockets: Infinity,  maxFreeSockets: 256,  scheduling: "lifo",  maxTotalSockets: Infinity,  totalSocketCount: 0,  maxCachedSessions: 100,  _sessionCache: { map: {}, list: [] },  [Symbol(kCapture)]: false}
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第 18、40 行,keepAlive 默认设置为 false;

V19
% nvm use 19Now using node v19.0.0 (npm v8.19.2)% node serverAgent {  _events: [Object: null prototype] {    free: [Function (anonymous)],    newListener: [Function: maybeEnableKeylog]  },  _eventsCount: 2,  _maxListeners: undefined,  defaultPort: 80,  protocol: "http:",  options: [Object: null prototype] {    keepAlive: true,    scheduling: "lifo",    timeout: 5000,    noDelay: true,    path: null  },  requests: [Object: null prototype] {},  sockets: [Object: null prototype] {},  freeSockets: [Object: null prototype] {},  keepAliveMsecs: 1000,  keepAlive: true,  maxSockets: Infinity,  maxFreeSockets: 256,  scheduling: "lifo",  maxTotalSockets: Infinity,  totalSocketCount: 0,  [Symbol(kCapture)]: false}Agent {  _events: [Object: null prototype] {    free: [Function (anonymous)],    newListener: [Function: maybeEnableKeylog]  },  _eventsCount: 2,  _maxListeners: undefined,  defaultPort: 443,  protocol: "https:",  options: [Object: null prototype] {    keepAlive: true,    scheduling: "lifo",    timeout: 5000,    noDelay: true,    path: null  },  requests: [Object: null prototype] {},  sockets: [Object: null prototype] {},  freeSockets: [Object: null prototype] {},  keepAliveMsecs: 1000,  keepAlive: true,  maxSockets: Infinity,  maxFreeSockets: 256,  scheduling: "lifo",  maxTotalSockets: Infinity,  totalSocketCount: 0,  maxCachedSessions: 100,  _sessionCache: { map: {}, list: [] },  [Symbol(kCapture)]: false}
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第 14、16、42、44 行设置 keepAlive 默认值及时间;

启用 keepAlive 能使连接重用,提高网络的吞吐量。

另外,服务器将在调用 close()自动断开空闲的客户端,内部依靠 http(s).Server.closeAPI 实现;

这些修改,进一步优化了体验和性能。

2. 稳定的 WebCrypto API

WebCrypto API 是一个使用密码学构建的系统接口,在 node.js v19 趋于稳定(除 Ed25519、Ed448、X25519、X448 外)。

我们可以通过调用 globalThis.cryptorequire("node:crypto").webcrypto来访问,下面以 subtle加密函数为例;

const { subtle } = globalThis.crypto;(async function() {  const key = await subtle.generateKey({    name: "HMAC",    hash: "SHA-256",    length: 256  }, true, ["sign", "verify"]);  console.log("key =", key);  const enc = new TextEncoder();  const message = enc.encode("I love cupcakes");  console.log("message =", message);  const digest = await subtle.sign({    name: "HMAC"  }, key, message);  console.log("digest =", digest);})();
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首先生成 HMAC 密钥,生成的密钥可同时用于验证消息数据完整性和真实性;

然后,对字符串 I love cupcakes加密;

最后创建 消息摘要,它是一种加密散列函数;

在控制台显示:key 、message 、digest 信息

% node serverkey = CryptoKey {  type: "secret",  extractable: true,  algorithm: { name: "HMAC", length: 256, hash: [Object] },  usages: [ "sign", "verify" ]}message = Uint8Array(15) [   73, 32, 108, 111, 118,  101, 32,  99, 117, 112,   99, 97, 107, 101, 115]digest = ArrayBuffer {  [Uint8Contents]: <30 01 7a 5c d9 e2 82 55 6b 55 90 4f 1d de 36 d7 89 dd fb fb 1a 9e a0 cc 5d d8 49 13 38 2f d1 bc>,  byteLength: 32}
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3. 自定义 ESM resolution 调整

Node.js 已经删除 --experimental-specifier-resolution ,其功能现在可以通过自定义加载器实现。

可以在这个库中测试:nodejs/loaders-test: Examples demonstrating the Node.js ECMAScript Modules Loaders API

git clone https://github.com/nodejs/loaders-test.git% cd loaders-test/commonjs-extension-resolution-loader% yarn install
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比如 loaders-test/commonjs-extension-resolution-loader/test/basic-fixtures/index.js 文件:

import { version } from "process";import { valueInFile } from "./file";import { valueInFolderIndex } from "./folder";console.log(valueInFile);console.log(valueInFolderIndex);
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./file如果没有自定义加载器,不会去查找文件的扩展名,比如 ./file.js./file.mjs

设置自定义加载器后,则可解决上述问题:

import { isBuiltin } from "node:module";import { dirname } from "node:path";import { cwd } from "node:process";import { fileURLToPath, pathToFileURL } from "node:url";import { promisify } from "node:util";import resolveCallback from "resolve/async.js";const resolveAsync = promisify(resolveCallback);const baseURL = pathToFileURL(cwd() + "/").href;export async function resolve(specifier, context, next) {  const { parentURL = baseURL } = context;  if (isBuiltin(specifier)) {    return next(specifier, context);  }  // `resolveAsync` works with paths, not URLs  if (specifier.startsWith("file://")) {    specifier = fileURLToPath(specifier);  }  const parentPath = fileURLToPath(parentURL);  let url;  try {    const resolution = await resolveAsync(specifier, {      basedir: dirname(parentPath),      // For whatever reason, --experimental-specifier-resolution=node doesn"t search for .mjs extensions      // but it does search for index.mjs files within directories      extensions: [".js", ".json", ".node", ".mjs"],    });    url = pathToFileURL(resolution).href;  } catch (error) {    if (error.code === "MODULE_NOT_FOUND") {      // Match Node"s error code      error.code = "ERR_MODULE_NOT_FOUND";    }    throw error;  }  return next(url, context);}
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测试命令:

% node --loader=./loader.js test/basic-fixtures/index  (node:56149) ExperimentalWarning: Custom ESM Loaders is an experimental feature. This feature could change at any time(Use `node --trace-warnings ...` to show where the warning was created)hello from file.js
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将不会再报错,正常运行。

4. 移除对 DTrace/SystemTap/ETW 支持

在 Node.js v19中,移除了对 DTrace/SystemTap/ETW 的支持,主要是因为资源的优先级问题。

数据表明很少人用到 DTrace、SystemTap 或 ETW,维护它们没有多大的意义。

如果你想恢复使用,可提 issues => github.com/nodejs/node…

5. 升级 V8 引擎至 10.7

Node.js v19 将 V8 JavaScript 引擎更新至 V8 10.7,其中包含一个新函数 Intl.NumberFormat,用于格式化敏感数字。

Intl.NumberFormat(locales, options)
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对于不同的语言,传入不同的 locales:

const number = 123456.789;console.log(new Intl.NumberFormat("de-DE", { style: "currency", currency: "EUR" }).format(number));console.log(new Intl.NumberFormat("ja-JP", { style: "currency", currency: "JPY" }).format(number));console.log(new Intl.NumberFormat("ar-SA", { style: "currency", currency: "EGP" }).format(number));console.log(new Intl.NumberFormat("zh-CN", { style: "currency", currency: "CNY" }).format(number));
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6. 试验 Node watch 模式

运行时增加了 node --watch 选项。

在 "watch" 模式下运行,当导入的文件被改变时,会重新启动进程。

比如:

const express = require("express");const path = require("path");const app = express();app.use(express.static(path.join(__dirname, "../build")));app.listen(8080, () =>  console.log("Express server is running on localhost:8080"));
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% node --watch server(node:67643) ExperimentalWarning: Watch mode is an experimental feature. This feature could change at any time(Use `node --trace-warnings ...` to show where the warning was created)Express server is running on localhost:8080
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Node.js 14 将在 2023 年 4 月结束更新维护,Node.js 16 (LTS) 预计将在 2023 年 9 月结束更新维护。

建议大家开始计划将版本按需升级到 Node.js 16(LTS)或 Node.js 18(LTS)。

更多node相关知识,请访问:nodejs 教程!

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