nodejs implements the function that a user can only like once

In order to allow users to better participate and interact, many websites will add functions such as likes and comments, so that users can interact with the content they are interested in. However, if there are no restrictions, users can like unlimitedly, which will lose the meaning of likes and even cause unnecessary trouble. Therefore, we need a way to implement the function of limiting users to one like.

In this article, we will use Node.js to implement a function that only allows users to like once. Before we get started, let’s take a look at the techniques and tools we need to use.

Node.js is a JavaScript runtime environment based on the Chrome V8 engine for developing high-performance web applications. It provides the infrastructure and libraries for writing server-side JavaScript code, making it easy to write efficient web applications.

Express is a popular Node.js web framework. It provides a series of functions such as routing, error handling, and rendering views based on HTTP requests, allowing us to quickly build a scalable web application.

MongoDB is a non-relational database management system that uses a document storage model and can support many different data types. It is a high-performance, scalable database that can be used to handle complex data storage and management.

Now let’s start implementing our function. First, we need to build a new Express application, using the following command:

mkdir nodejs-like-demo
cd nodejs-like-demo
npm init  // 创建 package.json 文件
npm install express --save

After completing the installation of Express, we need to add the following code to the application to set up routing and processors:

const express = require('express');
const app = express();

app.get('/', (req, res) => {
    res.send('Hello, world!');
});

app.listen(3000, () => {
    console.log('Server is running on port 3000');
});

This code will create a simple route and handler for sending a simple "Hello, world!" message to the user. Now we can start the application using the following command:

node app.js

Next, we need to create a database to store our user and like data. We can use MongoDB database to store data. First, we need to install MongoDB using the following command:

brew install mongodb

Then, we need to create a database to store our data. We can use the following command to create a database:

mongo
> use nodejs-like-demo

Next, we need to create a collection named users to store user data:

> db.createCollection('users')

Then, we need to create a collection named It is a collection of likes, used to store like data:

> db.createCollection('likes')

Now that we have completed the database settings, we need to create a route to handle the user's like request. We can add a new route handler using the following code:

app.post('/like', (req, res) => {
    const userId = req.body.userId;
    const postId = req.body.postId;
    const like = {
        userId: userId,
        postId: postId
    };
    const likes = db.collection('likes');
    const filter = { userId: userId, postId: postId };
    likes.findOne(filter, (err, result) => {
        if (result) {
            res.status(400).send('You already liked this post');
        } else {
            likes.insertOne(like, (err, result) => {
                if (err) {
                    console.log(err);
                    res.status(500).send('Internal Server Error');
                } else {
                    res.send('Success');
                }
            });
        }
    });
});

In this code, we first get the user ID and post ID, and then create a like object. We use the MongoDB database's collection object to get our likes collection and check if the user has already liked the post. If the user has already liked the post, send an error message, otherwise insert the like into the database.

Now that we have completed all the necessary code, we can start the application using the following command and send a POST request to our new endpoint through tools such as postman:

node app.js

Now, we can use The following command sends a POST request to the server:

curl --header "Content-Type: application/json" 
  --request POST 
  --data '{"userId":"1", "postId":"1"}' 
  http://localhost:3000/like

In this way, we have completed the function that a user can only like once. In actual applications, we can use more technologies and tools to improve this function. For example, we can use JWT to verify whether the user is a logged in user, or use an in-memory caching system such as Redis to speed up data access, etc.

In short, Node.js provides many powerful tools and technologies that can help us quickly build high-performance web applications and implement complex functions such as users who can only like once. Just by using these tools and technologies, we can easily implement the function that a user can only like once, providing users with a better experience and interaction.

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