Ajax基础原理与应用

Ajax函数封装ajax.js

// Get / Post
// 参数 get post
// 是否异步
// 如何处理响应数据
// URL

// var handleResponse = function(response) {
//
// }
// ajax.get('demo1.php', 'name=zhangsan&age=20', handleResponse, true)
// ajax.post('demo1.php', 'name=zhangsan&age=20', handleResponse, true)
function Ajax()
{
    // 初始化方法
    this.init = function()
    {
        this.xhr = new XMLHttpRequest();
    };

    // get请求方法
    this.get = function(url, parameters, callback, async = true)
    {
        this.init();
        if (async) {
            // 异步请求
            this.xhr.onreadystatechange = function() {
                // this => this.xhr
                if (this.readyState == 4 && this.status == 200) {
                    callback(this.responseText);
                }
            }
        }
        this.xhr.open('GET', url + '?' + parameters, async);
        this.xhr.send();
    };

    // post请求方法
    this.post = function(url, parameters, callback, async = true)
    {
        this.init();
        if (async) {
            // 异步请求
            this.xhr.onreadystatechange = function ()
            {
                if (this.readyState == 4 && this.status == 200) {
                    callback(this.responseText);
                }
            }
        }
        this.xhr.open('POST', url, async);
        this.xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
        this.xhr.send(parameters);
    }
}

var ajax = new Ajax();

调用演示

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <button id="btn">请求</button>
    <div id="container"></div>
    <script src="ajax.js"></script>
    <script>
        var btn = document.getElementById('btn');
        var container = document.getElementById('container');
        btn.onclick = function() {
                ajax.post('demo2.php', 'name=zhangsan&age=20', function(data) {
            container.innerHTML = data;
                });
        }
    </script>
</body>
</html>

Ajax类封装ajax2.0.js

// 通过class定义类
class Ajax
{
    // 构造方法
    constructor()
    {
        this.xhr = new XMLHttpRequest()
    }

    // 内部方法，不加function
    get(url, parameters, callback, async = true)
    {
        if (async) {
            this.xhr.onreadystatechange = () => {
                if (this.xhr.readyState == 4 && this.xhr.status == 200) {
                    callback(this.xhr.responseText)
                }
            }
            // this.xhr.onreadystatechange = function() {
            //     if (this.readyState == 4 && this.status == 200) {
            //         callback(this.responseText)
            //     }
            // }
        }
        this.xhr.open('GET', url + '?' + parameters, async)
        this.xhr.send()
    }

    // 内部方法，不加function
    post(url, parameters, callback, async = true)
    {
        if (async) {
            this.xhr.onreadystatechange = () => {
                if (this.xhr.readyState == 4 && this.xhr.status == 200) {
                    callback(this.xhr.responseText)
                }
            }
            // this.xhr.onreadystatechange = function() {
            //     if (this.readyState == 4 && this.status == 200) {
            //         callback(this.responseText)
            //     }
            // }
        }
        this.xhr.open('POST', url, async)
        this.xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded')
        this.xhr.send(parameters)
    }

}

let ajax = new Ajax()

调用演示

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script src="ajax2.0.js"></script>
<script>
    ajax.get('demo1.php', 'course=ajax', function(data) {
        console.log(data)
    })
</script>
</body>
</html>

Ajax方式实现分页

带搜索功能

首先是ajax类的封装Ajax.js

let $ = new class {

    constructor()
    {
        this.xhr = new XMLHttpRequest();
        this.xhr.onreadystatechange = () => {
            if (this.xhr.readyState == 4 && this.xhr.status == 200) {
                // process response text
                let response = this.xhr.responseText;
                if (this.type == "json") {
                    response = JSON.parse(response);
                }
                this.callback(response);
            }
        }
    }

    get(url, parameters, callback, type = "text")
    {
        // url = test.php?username=zhangsan&age=20
        // parameters = {"username": "zhangsan", "age": 20}
        let data = this.parseParameters(parameters);
        if (data.length > 0) {
            url += "?" + data;
        }
        this.type = type;
        this.callback = callback;
        this.xhr.open("GET", url, true);
        this.xhr.send();
    }

    post(url, parameters, callback, type = "text")
    {
        let data = this.parseParameters(parameters);
        this.type = type;
        this.callback = callback;
        this.xhr.open("POST", url, true);
        this.xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
        this.xhr.send(data);
    }

    parseParameters(parameters)
    {
        // username=zhangsan&age=20
        let buildStr = "";
        for (let key in parameters) {
            let str = key + "=" + parameters[key];
            buildStr += str + "&";
        }
        return buildStr.substring(0, buildStr.length - 1);
    }
};

前端页面

<!doctype html>
<html lang="en">
<head>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
    <title>test Users</title>
</head>
<body>
    <header>
        <nav class="navbar navbar-expand-lg navbar-light bg-light">
            <a class="navbar-brand" href="#">Users List</a>
            <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
                <span class="navbar-toggler-icon"></span>
            </button>

            <div class="collapse navbar-collapse" id="navbarSupportedContent">
                <ul class="navbar-nav mr-auto"></ul>
                <form class="form-inline my-2 my-lg-0" onsubmit="return false;">
                    <input class="form-control mr-sm-2 keywords" type="search" placeholder="Search" aria-label="Search" value="">
                    <button class="btn btn-outline-success my-2 my-sm-0 searchBtn" type="submit">Search</button>
                </form>
            </div>
        </nav>
    </header>

    <!-- data -->
    <div class="container" style="margin-top: 10px">
        <h2>test Users</h2>
        <table class="table table-striped">
            <thead>
            <tr>
                <th scope="col">#</th>
                <th scope="col">Username</th>
                <th scope="col">Age</th>
                <th scope="col">Gender</th>
                <th scope="col">Phone</th>
                <th scope="col">Address</th>
                <th scope="col">Created_at</th>
            </tr>
            </thead>
            <tbody></tbody>
        </table>
        <!-- Pagination-->
        <nav aria-label="Page navigation example">
            <ul class="pagination"></ul>
        </nav>
    </div>


<!-- Optional JavaScript -->
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
<script src="../library/Ajax.js"></script>
<script>
    let pageNo = 1;
    let kws = '';
    let searchBtn = document.getElementsByClassName('searchBtn')[0];
    searchBtn.onclick = function() {
        let search = document.getElementsByClassName('keywords')[0];
        let keywords = search.value;
        requestData(pageNo, keywords);
        kws = keywords;
    };

    let requestPage = function(page) {
        requestData(page, kws);
        pageNo = page;
    };

    let requestData = function(page_number, keywords) {
        let pagination = document.getElementsByClassName('pagination')[0];
        let tbody = document.getElementsByTagName('tbody')[0];
        tbody.innerHTML = '<tr><td colspan="7" class="text-center"><i class="fa fa-spinner fa-spin" style="font-size:24px"></i> 加载中...</td></tr>'
        $.get('users.php', {"page": page_number, "keywords": keywords}, function (res) {
            let trs = '';
            if (res.code == 1) {
                // 请求成功
                res.rows.forEach(function (item) {
                    let tr = '<tr><th scope="row">' + item.id + '</th>' +
                        '<td>' + item.username + '</td>' +
                        '<td>' + item.age + '</td>' +
                        '<td>' + item.gender + '</td>' +
                        '<td>' + item.phone + '</td>' +
                        '<td>' + item.address + '</td>' +
                        '<td>' + item.created_at + '</td>' +
                        '</tr>';
                    trs += tr;
                });
                tbody.innerHTML = trs;

                // 加载页码导航
                // previous
                let previousBtn = '';
                if (res.page_number == 1) {
                    previousBtn = '<li class="page-item disabled"><a class="page-link" href="javascript:requestPage(' + (res.page_number - 1) + ');">Previous</a></li>';
                } else {
                    previousBtn = '<li class="page-item"><a class="page-link" href="javascript:requestPage(' + (res.page_number - 1) + ');">Previous</a></li>';
                }
                // next
                let nextBtn = '';
                if (res.page_total == res.page_number) {
                    nextBtn = '<li class="page-item disabled"><a class="page-link" href="javascript:requestPage(' + (res.page_number + 1) + ');">Next</a></li>';
                } else {
                    nextBtn = '<li class="page-item"><a class="page-link" href="javascript:requestPage(' + (res.page_number + 1) + ');">Next</a></li>'
                }

                let pages = previousBtn;
                for (let page = 1; page <= res.page_total; page++) {
                    let active = '';
                    if (page == res.page_number) {
                        active = 'active';
                    }
                    pages += '<li class="page-item ' + active + '"><a class="page-link" href="javascript:requestPage(' + page + ');">' + page + '</a></li>';
                }
                pages += nextBtn;
                pagination.innerHTML = pages;
            }
        }, 'json');
    };
    requestData(1, '');
</script>
</body>
</html>

users.php

<?php
/**
 * Created by PhpStorm.
 * User: JasonLee
 * Date: 2018/12/1
 * Time: 18:27
 */
// 请求数据库，响应对应页码的数据
// PDO

// 接收请求数据
$pageNo = $_GET['page'] ?? 1;
$pageSize = 5;

// 接收查询参数
$keywords = $_GET['keywords'] ?? '';

// 1 -- 0
// 2 -- 5
// 3 -- 10


$data = [];
try {
    $pdo = new PDO('mysql:host=localhost:3306;dbname=test_ajax_pager',
        'root',
        '123456',
        [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]
    );

    // 请求mysql 查询记录总数
    $sql = 'SELECT count(*) AS aggregate FROM test_users';
    if (strlen($keywords) > 0) {
        $sql .= ' WHERE username like ?';
    }
    $stmt = $pdo->prepare($sql);
    if (strlen($keywords) > 0) {
        $stmt->bindValue(1, '%' . $keywords . '%', PDO::PARAM_STR);
    }
    $stmt->execute();
    $total = $stmt->fetch(PDO::FETCH_ASSOC)['aggregate'];

    // 计算最大页码，设置页码边界
    $minPage = 1;
    $maxPage = ceil($total / $pageSize); // 3.6
    $pageNo = max($pageNo, $minPage);
    $pageNo = min($pageNo, $maxPage);
    $offset = ($pageNo - 1) * $pageSize;

    $sql = 'SELECT id, username, age, gender, phone, address, created_at FROM test_users';
    if (strlen($keywords) > 0) {
        $sql .= ' WHERE username like ?';
    }
    $sql .= ' LIMIT ?, ?';
    $stmt = $pdo->prepare($sql);
    if (strlen($keywords) > 0) {
        $stmt->bindValue(1, '%' . $keywords . '%', PDO::PARAM_STR);
        $stmt->bindValue(2, (int)$offset, PDO::PARAM_INT);
        $stmt->bindValue(3, (int)$pageSize, PDO::PARAM_INT);
    } else {
        $stmt->bindValue(1, (int)$offset, PDO::PARAM_INT);
        $stmt->bindValue(2, (int)$pageSize, PDO::PARAM_INT);
    }
    $stmt->execute();
    $results = $stmt->fetchAll(PDO::FETCH_ASSOC);
    $data = [
        'code' => 1,
        'msg' => 'ok',
        'rows' => $results,
        'total_records' => (int)$total,
        'page_number' => (int)$pageNo,
        'page_size' => (int)$pageSize,
        'page_total' => (int)$maxPage,
    ];

} catch (PDOException $e) {
    $data = [
        'code' => 0,
        'msg' => $e->getMessage(),
        'rows' => [],
        'total_records' => 0,
        'page_number' => 0,
        'page_size' => (int)$pageSize,
        'page_total' => 0,
    ];
}

header('Content-type: application/json');
echo json_encode($data);

数据库结构test_ajax_pager.sql

/*
 Navicat MySQL Data Transfer

 Source Server         : 127.0.0.1
 Source Server Type    : MySQL
 Source Server Version : 80012
 Source Host           : localhost:3306
 Source Schema         : test_ajax_pager

 Target Server Type    : MySQL
 Target Server Version : 80012
 File Encoding         : 65001

 Date: 18/11/2018 10:56:13
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for test_users
-- ----------------------------
DROP TABLE IF EXISTS `test_users`;
CREATE TABLE `test_users` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `username` varchar(50) NOT NULL DEFAULT '',
  `age` tinyint(4) NOT NULL DEFAULT '1',
  `gender` varchar(30) NOT NULL DEFAULT 'Not Specified',
  `phone` varchar(50) NOT NULL DEFAULT '',
  `address` varchar(255) NOT NULL DEFAULT '',
  `created_at` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of test_users
-- ----------------------------
BEGIN;
INSERT INTO `test_users` VALUES (1, 'zhangsan', 20, 'Male', '13888888888', 'Chaoyang Beijing', '2018-11-18 09:52:23');
INSERT INTO `test_users` VALUES (2, 'lisi', 30, 'Female', '13899999999', 'Haidian Beijing', '2018-11-18 09:53:30');
INSERT INTO `test_users` VALUES (3, 'wangwu', 32, 'Male', '13877777777', 'Changping Beijing', '2018-11-18 09:54:15');
INSERT INTO `test_users` VALUES (4, 'zhaoliu', 28, 'Male', '13866666666', 'Shunyi Beijing', '2018-11-18 09:54:34');
INSERT INTO `test_users` VALUES (5, 'tianqi', 23, 'Not Specified', '13855555555', 'Changping Beijing', '2018-11-18 09:55:18');
INSERT INTO `test_users` VALUES (6, 'liba', 33, 'Female', '13844444444', 'Chaoyang Beijing', '2018-11-18 09:55:53');
INSERT INTO `test_users` VALUES (7, 'wangjiu', 45, 'Not Specified', '13833333333', 'Hongkou Shanghai', '2018-11-18 09:56:21');
INSERT INTO `test_users` VALUES (8, 'wanger', 26, 'Male', '13777777777', 'Hangzhou', '2018-11-18 09:57:10');
INSERT INTO `test_users` VALUES (9, 'liyi', 25, 'Not Specified', '13555555555', 'Shanghai', '2018-11-18 09:58:38');
INSERT INTO `test_users` VALUES (10, 'zhangxiaosan', 21, 'Not Specified', '13111111111', 'Beijing', '2018-11-18 09:59:09');
INSERT INTO `test_users` VALUES (11, 'lixiaosi', 32, 'Male', '13222222222', 'Shanghai', '2018-11-18 09:59:30');
INSERT INTO `test_users` VALUES (12, 'wangxiaowu', 33, 'Not Specified', '13812345678', 'Beijing', '2018-11-18 10:01:44');
INSERT INTO `test_users` VALUES (13, 'zhaoxiaoliu', 44, 'Not Specified', '13612345678', 'Shanghai', '2018-11-18 10:02:10');
INSERT INTO `test_users` VALUES (14, 'tianxiaoqi', 52, 'Female', '18612345678', 'Beijing', '2018-11-18 10:02:35');
INSERT INTO `test_users` VALUES (15, 'lixiaoba', 36, 'Not Specified', '18712345678', 'Shanghai', '2018-11-18 10:02:57');
INSERT INTO `test_users` VALUES (16, 'wangxiaojiu', 42, 'Not Specified', '18212345678', 'Hangzhou', '2018-11-18 10:03:23');
INSERT INTO `test_users` VALUES (17, 'wangxiaoer', 31, 'Male', '18512345678', 'Suzhou', '2018-11-18 10:03:51');
INSERT INTO `test_users` VALUES (18, 'lixiaoyi', 28, 'Female', '18787654321', 'Guangzhou', '2018-11-18 10:04:22');
COMMIT;

SET FOREIGN_KEY_CHECKS = 1;
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原文地址：https://www.cnblogs.com/chenyingying0/p/12190493.html