Node.js Backend Development Bootcamp · 课时

处理请求数据：正文、查询与参数

掌握 Express 如何接收并解析客户端传入的数据，包括路由参数、查询字符串、JSON 正文和表单提交。

处理请求数据：正文、查询与参数 是 CoddyKit 上的免费 Node.js Backend Development Bootcamp 课时。这是第 4 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 Node.js Backend Development Bootcamp 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Node.js Backend Development Bootcamp 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Where Client Data Comes From

An HTTP request can carry data in several places. An Express handler reads each from a different property of the req object:

Route params: req.params
Query string: req.query
Request body: req.body
Headers: req.headers

app.get('/info', (req, res) => {
  res.json({ params: req.params, query: req.query });
});

Route Parameters

Route parameters are named URL segments prefixed with a colon. For /users/:id, a request to /users/42 gives req.params.id === '42'.

They are always strings, so convert to numbers when needed.

app.get('/users/:id', (req, res) => {
  const id = Number(req.params.id);
  res.send('Looking up user ' + id);
});

Multiple Route Parameters

A route can capture several params at once. Each colon segment becomes a key on req.params.

app.get('/books/:author/:title', (req, res) => {
  const { author, title } = req.params;
  res.send(author + ' wrote ' + title);
});

Query Strings

Everything after the ? in a URL is the query string. Express parses it into req.query as key-value pairs.

For /search?term=node&page=2, you get req.query.term and req.query.page.

app.get('/search', (req, res) => {
  const { term, page } = req.query;
  res.send('Searching ' + term + ' page ' + (page || 1));
});

Parsing JSON Bodies

POST and PUT requests usually send a JSON body. Express does not parse it by default — you must enable the built-in middleware express.json().

const express = require('express');
const app = express();
app.use(express.json());
app.post('/users', (req, res) => {
  res.json({ received: req.body });
});

Parsing Form Data

HTML forms submit data as application/x-www-form-urlencoded. Enable express.urlencoded() to populate req.body from form fields.

app.use(express.urlencoded({ extended: true }));
app.post('/login', (req, res) => {
  res.send('Welcome ' + req.body.username);
});

Validating Required Fields

Never trust client input. Always check that required fields are present before using them, and respond with a 400 Bad Request if something is missing.

app.post('/users', (req, res) => {
  const { name, email } = req.body;
  if (!name || !email) {
    return res.status(400).json({ error: 'name and email required' });
  }
  res.status(201).json({ name, email });
});

Reading Headers

Headers carry metadata like authentication tokens and content types. Access them via req.headers (keys are lowercased) or the helper req.get().

app.get('/secure', (req, res) => {
  const auth = req.get('Authorization');
  res.send('Token: ' + (auth || 'none'));
});

Default Values for Optional Data

Query and body values are often optional. Provide sensible defaults so your handler does not break when a parameter is omitted.

app.get('/products', (req, res) => {
  const page = Number(req.query.page) || 1;
  const limit = Number(req.query.limit) || 10;
  res.json({ page, limit });
});

Combining All Three Sources

A single endpoint can read params, query, and body together. For example, updating a resource identified by a param, with options in the query, and new data in the body.

app.put('/users/:id', (req, res) => {
  const id = req.params.id;
  const notify = req.query.notify === 'true';
  const updates = req.body;
  res.json({ id, notify, updates });
});

Common Mistakes

Watch out for these pitfalls:

Forgetting express.json() so req.body is undefined
Treating params as numbers without converting
Trusting input without validation
Confusing query (?key=value) with params (/:key)

Quick Check

Test your knowledge of Express request data.

Recap

You now know how Express receives client data:

req.params for named URL segments
req.query for the query string
req.body for JSON (with express.json()) and forms (with express.urlencoded())
req.headers / req.get() for metadata

Always validate and provide defaults — never trust raw client input.

常见问题解答

「处理请求数据：正文、查询与参数」课时是免费的吗？

是的 — 「处理请求数据：正文、查询与参数」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Node.js Backend Development Bootcamp 课程的其余内容，请升级到 CoddyKit PRO。 Node.js Backend Development Bootcamp 课程共包含 4 节课。

「处理请求数据：正文、查询与参数」这节课中我会学到什么？

掌握 Express 如何接收并解析客户端传入的数据，包括路由参数、查询字符串、JSON 正文和表单提交。你通过在浏览器中直接运行的动手代码来练习 Node.js Backend Development Bootcamp，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Node.js Backend Development Bootcamp 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Node.js Backend Development Bootcamp 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 4 节课，共 4 节。

「处理请求数据：正文、查询与参数」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Node.js Backend Development Bootcamp 课中编写并运行代码吗？

能。每节 Node.js Backend Development Bootcamp 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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