How to access the database with jquery

jQuery is a popular JavaScript library used to simplify tasks such as HTML event handling, DOM manipulation, AJAX calls, etc. in the page. Although jQuery itself does not provide direct access to the database, you can access the database by referencing other JavaScript libraries and using server-side scripting languages.

1. Use AJAX to call the back-end interface

You can call the back-end interface through AJAX technology, and then access the database through these interfaces. When using AJAX, you need to transfer the parameters of the call to the backend, wait for the backend processing to complete, return the data to the frontend, and then render the data to the page through jQuery.

On the backend, database access libraries in PHP, Node.js, Python and other languages ​​can be used to handle database access tasks. For example, use the mongoose library in Node.js to access the MongoDB database and return the data to the front end in JSON format:

// 后端代码
var mongoose = require('mongoose')
var db = mongoose.createConnection('mongodb://localhost/test')
var User = db.model('User', {username: String, age: Number})

app.get('/user', function(req, res) {
    User.find({}).exec(function(err, result) {
        if (err) throw err
        res.json(result)
    })
})

As you can see, the above code is created using the Express framework in Node.js A route that listens to the '/user' path. When a request comes, it will access MongoDB through the mongoose library, find all user data, and return it to the front end using the res.json method.

The front end can use jQuery to initiate AJAX requests and render the returned data into the page. For example:

// 前端代码
$.ajax({
    url: '/user',
    type: 'GET',
    success: function(data) {
        // 渲染数据
        var html = ''
        for (var i = 0; i < data.length; i++) {
            var user = data[i]
            html += '<tr><td>' + user.username + '</td><td>' + user.age + '</td></tr>'
        }
        $('.user-table').append(html)
    }
})

In the above jQuery code, AJAX is used to call the back-end interface, read all user data, and then render the data into a table on the page.

2. Use jQuery plug-ins

In addition to AJAX technology, there are also some jQuery plug-ins that can directly access the database. For example, you can use the DataTabels plug-in to work with tabular data and directly access data in a database.

When using DataTables, you need to obtain data from the backend, and then perform operations such as paging, sorting, and searching on the client. You can assign the JSON data returned by the server to the data attribute of DataTables, and then render the data through DataTables on the page.

The following is a sample code for using DataTables to render a table:

// 前端代码
$(document).ready(function() {
    $('#user-table').DataTable({
        "processing": true,
        "serverSide": true,
        "ajax": {
            "url": "/user",
            "type": "POST"
        },
        "columns": [
            { "data": "username" },
            { "data": "age" },
        ]
    })
})

3. Use the ORM framework

The ORM (Object-Relational Mapping) framework can avoid problems caused by directly operating the database A series of problems have shifted the task of operating the database to the back end. The ORM framework can directly operate the database and encapsulate the data into object form to facilitate data rendering on the front end.

In Node.js, the ORM function can be implemented using the Sequelize module. Using Sequelize can create models, data migration, queries and other operations, allowing users to easily perform CRUD (Create, Read, Update, Delete) operations on data.

The following is a sample code that uses Sequelize to implement ORM:

// 后端代码
const Sequelize = require('sequelize')
const sequelize = new Sequelize('mysql://root:123456@localhost:3306/test')

const User = sequelize.define('user', {
    username: Sequelize.STRING,
    age: Sequelize.INTEGER
})

app.get('/users', async (req, res) => {
    const users = await User.findAll()
    res.json(users)
})

// 前端代码
$.ajax({
    url: '/users',
    type: 'GET',
    success: function(data) {
        // 渲染数据
        var html = ''
        for (var i = 0; i < data.length; i++) {
            var user = data[i]
            html += '<tr><td>' + user.username + '</td><td>' + user.age + '</td></tr>'
        }
        $('.user-table').append(html)
    }
})

4. Summary

In actual projects, accessing the database usually requires operations through the background. Data can be obtained from the backend more easily through AJAX and jQuery plug-ins. When using the ORM framework, you only need to operate objects to perform CRUD operations, which reduces the problems caused by directly operating the database and facilitates maintenance and management of developers. .

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