Node.js day2:Koa概念

19_Node.js/Koa快速入门.md

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+# Koa快速入门
+
+## 1. Koa 是什么？
+
+> Koa 是 基于Node.js平台的下一代Web开发框架（上一代 就是 Express）。
+
+## 2. 基本使用
+
+```js
+import Koa from 'koa';
+import { PORT, HOST } from './config/system.mjs';
+
+const app = new Koa();
+
+app.use((ctx) => {
+  ctx.body = 'Hello, Koa.';
+});
+
+app.listen(PORT, HOST, () => {
+  console.log(`服务已启动，URL地址为：${'http://' + HOST + ':' + PORT}`);
+});
+```
+
+引入 Koa 类后，通过 `new Koa()`创建app实例。然后在调用对应`listen`方法去监听一个端口号，如果没有报错，即服务启动成功。
+
+然后 `app.use()`方法是给Koa应用程序添加中间件。作用是给所有请求响应数据的。
+
+## 3. 相关概念
+
+### 3.1 中间件
+
+> 本质 就是 JavaScript函数。会接受一个参数`ctx`，即上下文对象（整合了Node.js中的request和response两个对象）以及 第二个参数`next`，即为栈中的下一个中间件函数。
+>
+> - 可以在整个请求/响应循环周期内 做任何事情。
+> - 还可以修改ctx对象，比如添加路由间共享的数据等
+> - 结束请求/响应周期（结束响应）
+> - 调用下一个中间件
+
+### 3.2 context对象
+
+> Koa Context 将 node 的 `request` 和 `response` 对象封装到单个对象中，为编写 Web 应用程序和 API 提供了许多有用的方法。
+
+- `ctx.query` 获取请求URL地址上的查询参数，返回一个Object对象。
+- `ctx.body=` 设置响应正文，同时会结束请求/响应周期
+- `ctx.status=` 设置HTTP状态码，比如: `ctx.status = 200;`
+- `ctx.message=` 设置HTTP状态信息
+- `ctx.length=` 设置 Content-Length 响应头
+- `ctx.type=` 设置 Content-Type 响应头

19_Node.js/day-2/code/koa-app/config/system.mjs

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+export const PORT = 4000;
+export const HOST = 'localhost';

19_Node.js/day-2/code/koa-app/index.js

@@ -0,0 +1,19 @@
+import Koa from 'koa';
+import { PORT, HOST } from './config/system.mjs';
+
+const app = new Koa();
+
+app.use((ctx) => {
+  // 该 中间间 作用就是 给予客户端响应 并结束响应循环。
+  ctx.status = 200;
+  ctx.message = 'OKK';
+  ctx.type = 'application/json';
+  // ctx.body = 'Hello, Koa.';
+  ctx.body = { code: 0, data: [], msg: 'okk' };
+
+  console.log('请求参数', ctx.query);
+});
+
+app.listen(PORT, HOST, () => {
+  console.log(`服务已启动，URL地址为：${'http://' + HOST + ':' + PORT}`);
+});

19_Node.js/day-2/code/koa-app/package-lock.json

@@ -0,0 +1,406 @@
+{
+  "name": "koa-app",
+  "version": "1.0.0",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "koa-app",
+      "version": "1.0.0",
+      "license": "ISC",
+      "dependencies": {
+        "koa": "^2.14.2"
+      }
+    },
+    "node_modules/accepts": {
+      "version": "1.3.8",
+      "resolved": "https://registry.npmmirror.com/accepts/-/accepts-1.3.8.tgz",
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+      "dependencies": {
+        "mime-types": "~2.1.34",
+        "negotiator": "0.6.3"
+      },
+      "engines": {
+        "node": ">= 0.6"
+      }
+    },
+    "node_modules/cache-content-type": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmmirror.com/cache-content-type/-/cache-content-type-1.0.1.tgz",
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+      "resolved": "https://registry.npmmirror.com/content-disposition/-/content-disposition-0.5.4.tgz",
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+      },
+      "engines": {
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+      }
+    },
+    "node_modules/content-type": {
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+      "engines": {
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+        "keygrip": "~1.1.0"
+      },
+      "engines": {
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+      }
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+      },
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+        }
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+    "node_modules/setprototypeof": {
+      "version": "1.2.0",
+      "resolved": "https://registry.npmmirror.com/setprototypeof/-/setprototypeof-1.2.0.tgz",
+      "integrity": "sha512-E5LDX7Wrp85Kil5bhZv46j8jOeboKq5JMmYM3gVGdGH8xFpPWXUMsNrlODCrkoxMEeNi/XZIwuRvY4XNwYMJpw=="
+    },
+    "node_modules/statuses": {
+      "version": "1.5.0",
+      "resolved": "https://registry.npmmirror.com/statuses/-/statuses-1.5.0.tgz",
+      "integrity": "sha512-OpZ3zP+jT1PI7I8nemJX4AKmAX070ZkYPVWV/AaKTJl+tXCTGyVdC1a4SL8RUQYEwk/f34ZX8UTykN68FwrqAA==",
+      "engines": {
+        "node": ">= 0.6"
+      }
+    },
+    "node_modules/toidentifier": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmmirror.com/toidentifier/-/toidentifier-1.0.1.tgz",
+      "integrity": "sha512-o5sSPKEkg/DIQNmH43V0/uerLrpzVedkUh8tGNvaeXpfpuwjKenlSox/2O/BTlZUtEe+JG7s5YhEz608PlAHRA==",
+      "engines": {
+        "node": ">=0.6"
+      }
+    },
+    "node_modules/tsscmp": {
+      "version": "1.0.6",
+      "resolved": "https://registry.npmmirror.com/tsscmp/-/tsscmp-1.0.6.tgz",
+      "integrity": "sha512-LxhtAkPDTkVCMQjt2h6eBVY28KCjikZqZfMcC15YBeNjkgUpdCfBu5HoiOTDu86v6smE8yOjyEktJ8hlbANHQA==",
+      "engines": {
+        "node": ">=0.6.x"
+      }
+    },
+    "node_modules/type-is": {
+      "version": "1.6.18",
+      "resolved": "https://registry.npmmirror.com/type-is/-/type-is-1.6.18.tgz",
+      "integrity": "sha512-TkRKr9sUTxEH8MdfuCSP7VizJyzRNMjj2J2do2Jr3Kym598JVdEksuzPQCnlFPW4ky9Q+iA+ma9BGm06XQBy8g==",
+      "dependencies": {
+        "media-typer": "0.3.0",
+        "mime-types": "~2.1.24"
+      },
+      "engines": {
+        "node": ">= 0.6"
+      }
+    },
+    "node_modules/vary": {
+      "version": "1.1.2",
+      "resolved": "https://registry.npmmirror.com/vary/-/vary-1.1.2.tgz",
+      "integrity": "sha512-BNGbWLfd0eUPabhkXUVm0j8uuvREyTh5ovRa/dyow/BqAbZJyC+5fU+IzQOzmAKzYqYRAISoRhdQr3eIZ/PXqg==",
+      "engines": {
+        "node": ">= 0.8"
+      }
+    },
+    "node_modules/ylru": {
+      "version": "1.3.2",
+      "resolved": "https://registry.npmmirror.com/ylru/-/ylru-1.3.2.tgz",
+      "integrity": "sha512-RXRJzMiK6U2ye0BlGGZnmpwJDPgakn6aNQ0A7gHRbD4I0uvK4TW6UqkK1V0pp9jskjJBAXd3dRrbzWkqJ+6cxA==",
+      "engines": {
+        "node": ">= 4.0.0"
+      }
+    }
+  }
+}

19_Node.js/day-2/code/koa-app/package.json

@@ -0,0 +1,17 @@
+{
+  "name": "koa-app",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "type": "module",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1",
+    "dev": "nodemon index.js"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "koa": "^2.14.2"
+  }
+}