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Ajax基础原理与应用

2020年01月14日  | 萬仟网IT编程  | 我要评论

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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