Examples to explain how to use nodejs to implement web page collection function

In recent years, with the continuous development of the Internet, data collection has become an indispensable job for many people. Among them, web page collection is a relatively common method. Node.js is a technology that is very suitable for web page collection.

1. What is Node.js?

Node.js is a cross-platform open source runtime environment for writing server-side code using JavaScript. It is based on the Chrome V8 engine, event-driven, non-blocking I/O model, and has the characteristics of high efficiency and lightweight.

2. Advantages of Node.js

Node.js’s non-blocking I/O model and event driver can handle high concurrency and large-scale requests. Through asynchronous I/O, a single thread can handle thousands of concurrent connections, and the response speed is very fast. At the same time, Node.js uses a single-threaded model, so there will be no performance problems caused by thread synchronization. At the same time, the modular design of Node.js makes the code simpler and easier to maintain.

3. Application of Node.js

1. Web application development

Node.js can be used to quickly develop high-performance web applications. Since JavaScript is a dynamic language, it can be easily programmed dynamically. The excellent asynchronous I/O characteristics of Node.js make it very suitable for developing real-time web applications.

2. Data collection

Since Node.js can use JavaScript to write server-side code, it is very suitable for data collection. Especially for scenarios that require crawling a large number of web pages, the asynchronous I/O feature of Node.js can better improve the collection efficiency.

4. Excellent case: Node.js implements web page collection

The asynchronous I/O feature of Node.js is very suitable for handling web page collection scenarios. Here, we can use a practical example to demonstrate how to use Node.js to implement web page collection.

Suppose we need to collect product information from an e-commerce website:

1. First, we need to use the request module to access the website and obtain the web page content.

const request = require('request');
const url = 'http://www.jd.com';
const options = {
    method: 'GET'
};
request(url, options, function(err, response, body) {
    if(err) {
        console.log(err);
    } else {
        console.log(body);
    }
});

2. Next, we need to use the cheerio module to parse the content of the web page. Cheerio is a library that can operate HTML/XML like jQuery. It provides a series of DOM operation methods and Traversing methods, which can easily locate HTML nodes.

const cheerio = require('cheerio');
const $ = cheerio.load(body);
const goodsList = $('.goods-list li');
goodsList.each(function() {
    const goodsItem = $(this);
    const goodsTitle = goodsItem.find('.goods-title').text();
    const goodsPrice = goodsItem.find('.goods-price').text();
    console.log(goodsTitle + ' ' + goodsPrice);
});

3. Finally, we can store the collected data in the database for subsequent analysis and processing.

const mysql = require('mysql');
const connection = mysql.createConnection({
    host: 'localhost',
    user: 'root',
    password: '',
    database: 'test'
});
goodsList.each(function() {
    const goodsItem = $(this);
    const goodsTitle = goodsItem.find('.goods-title').text();
    const goodsPrice = goodsItem.find('.goods-price').text();
    connection.query('INSERT INTO goods(title, price) VALUES(?, ?)', [goodsTitle, goodsPrice], function(err, result) {
        if(err) {
            console.log(err);
        }
    });
});

Through the above three steps, we can use Node.js to implement web page collection.

Summary: Node.js has excellent asynchronous I/O features and high performance, making it very suitable for web page collection. For different websites and needs, we can develop a variety of web page collection tools through the rich modules of Node.js.

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