jquery - 限制分页中可见页面的数量

Question

我正在开发一个 jQuery 分页工具，虽然分页工作正常，但我发现了一个缺陷:

在桌面上有一排 14 个以上的分页链接没问题，但在移动设备上就不行了。因此，我想将可见页面的数量一次限制为 5 个(不包括下一个/上一个按钮)，并在到达第三个可见页面时更新它，并更新分页中的可见页面，本质上看起来像

| Prev | 1 | ... | 3 | 4 | 5 | 6 | Next |

我写了this CodePen到目前为止我所拥有的。我知道有一些插件可以为我执行此操作，但我想避免在该项目中使用插件。

HTML(正在分页的示例内容)

<div class="container" id="jar">
    <div class="row content">
         <div class="col">
              <img src="http://via.placeholder.com/350x150">
         </div>
         <div class="col">
             <img src="http://via.placeholder.com/350x150">
         </div>
    </div>
</div>

HTML(分页元素)

 <nav>
   <ul class="pagination justify-content-center pagination-sm">
     <li id="previous-page" class="page-item"><a class="page-link" href="javascript:void(0)">Prev</a>
     </li>
   </ul>
 </nav>

JavaScript:

"use strict";
 //NOTE: the class"page-item page-link" are classes used in bootstrap 4 and will not be seen declared or used outside of the <li> as the bootstrap framework uses those classes to apply CSS

 //sets number of items and limits the number of items per page

var numberOfItems = $("#jar .content").length;
var limitPerPage = 2;

//as the items start at 0 to keep the items per page at the limitPerPage set in variable, need to subtract 1 as is shown below

$("#jar .content:gt(" + (limitPerPage - 1) + ")").hide();

//sets total pages rounded to the next whole number

var totalPages = Math.round(numberOfItems / limitPerPage);

//append the 1 page to the pagination

$(".pagination").append(
        "<li class='page-item current-page active'><a class='page-link'  href='javascript:void(0)'>" +
        1 +
        "</a></li>"
        );

//append the pages in sequential order after prev button (as seen in the html in codepen)

for (var i = 2; i <= totalPages; i++) {
    $(".pagination").append(
            "<li class='page-item current-page'><a class='page-link' href='javascript:void(0)'>" +
            i +
            "</a></li>"
            );
}

//appends the next button link as the final child element in the pagination

$(".pagination").append(
        "<li class='page-item' id='next-page'><a class='page-link' href='javascript:void(0)'>Next</a></li>"
        );

//When a page is selected, if it has "active" class return false, if no "active" class, go to page and add "active" class attribute and remove from any other element that has "active" on it.

$(".pagination li.current-page").on("click", function () {
    if ($(this).hasClass("active")) {
        return false;
    } else {
        var currentPage = $(this).index();
        $(".pagination li").removeClass("active");
        $(this).addClass("active");
        $("#jar .content").hide();

       //.hide will hide content that does not fit into that page (ie 0 and 1 on page one, 2 and 3 on page two and so on will show on appropriate page)  If it does not fall within the range for that page .hide, if it falls within the range .show content

        var grandTotal = limitPerPage * currentPage;

        for (var i = grandTotal - limitPerPage; i < grandTotal; i++) {
            $("#jar .content:eq(" + i + ")").show();
        }
    }
});

//when next is clicked if it is on the last page, return false otherwise move on to next page in pagination and remove "active" class from previous page and add "active" class to new page

$("#next-page").on("click", function () {
    var currentPage = $(".pagination li.active").index();
    if (currentPage === totalPages) {
        return false;
    } else {
        currentPage++;
        $(".pagination li").removeClass("active");
        $("#jar .content").hide();

        var grandTotal = limitPerPage * currentPage;

        for (var i = grandTotal - limitPerPage; i < grandTotal; i++) {
            $("#jar .content:eq(" + i + ")").show();
        }
        $(".pagination li.current-page:eq(" + (currentPage - 1) + ")").addClass(
                "active"
                );
    }
});

//when prev is clicked if it is on the 1 page, return false otherwise move on to previous page and remove "active" class from last page visited and add "active" class to new page

$("#previous-page").on("click", function () {
    var currentPage = $(".pagination li.active").index();
    if (currentPage === 1) {
        return false;
    } else {
        currentPage--;
        $(".pagination li").removeClass("active");
        $("#jar .content").hide();

        var grandTotal = limitPerPage * currentPage;

        for (var i = grandTotal - limitPerPage; i < grandTotal; i++) {
            $("#jar .content:eq(" + i + ")").show();
        }
        $(".pagination li.current-page:eq(" + (currentPage - 1) + ")").addClass(
                "active"
                );
    }
});

Answer 1

我建议使用一个函数——给定当前页码、总页数以及您想要拥有的最大按钮数——将返回一个数字数组，其中 0 表示 ... 按钮，其他数字表示可点击的页面按钮。

例如，它可能返回:

[1, 2, 0, 5, 6, 7, 0, 10, 11]

...代表以下按钮:

1、2、...、5、6、 7、...、10、11

该函数将完成计算那些 ... 应该放置在哪里的艰苦工作，但是一旦你有了它，将它与你的页面集成起来就是小菜一碟。

以下示例将按钮数量(不包括 prev/next，包括 ... 按钮)限制为 7。如果您愿意，可以将该参数减少到 5:

// Returns an array of maxLength (or less) page numbers
// where a 0 in the returned array denotes a gap in the series.
// Parameters:
//   totalPages:     total number of pages
//   page:           current page
//   maxLength:      maximum size of returned array
function getPageList(totalPages, page, maxLength) {
    if (maxLength < 5) throw "maxLength must be at least 5";

    function range(start, end) {
        return Array.from(Array(end - start + 1), (_, i) => i + start); 
    }

    var sideWidth = maxLength < 9 ? 1 : 2;
    var leftWidth = (maxLength - sideWidth*2 - 3) >> 1;
    var rightWidth = (maxLength - sideWidth*2 - 2) >> 1;
    if (totalPages <= maxLength) {
        // no breaks in list
        return range(1, totalPages);
    }
    if (page <= maxLength - sideWidth - 1 - rightWidth) {
        // no break on left of page
        return range(1, maxLength - sideWidth - 1)
            .concat(0, range(totalPages - sideWidth + 1, totalPages));
    }
    if (page >= totalPages - sideWidth - 1 - rightWidth) {
        // no break on right of page
        return range(1, sideWidth)
            .concat(0, range(totalPages - sideWidth - 1 - rightWidth - leftWidth, totalPages));
    }
    // Breaks on both sides
    return range(1, sideWidth)
        .concat(0, range(page - leftWidth, page + rightWidth),
                0, range(totalPages - sideWidth + 1, totalPages));
}

// Below is an example use of the above function.
$(function () {
    // Number of items and limits the number of items per page
    var numberOfItems = $("#jar .content").length;
    var limitPerPage = 2;
    // Total pages rounded upwards
    var totalPages = Math.ceil(numberOfItems / limitPerPage);
    // Number of buttons at the top, not counting prev/next,
    // but including the dotted buttons.
    // Must be at least 5:
    var paginationSize = 7; 
    var currentPage;

    function showPage(whichPage) {
        if (whichPage < 1 || whichPage > totalPages) return false;
        currentPage = whichPage;
        $("#jar .content").hide()
            .slice((currentPage-1) * limitPerPage, 
                    currentPage * limitPerPage).show();
        // Replace the navigation items (not prev/next):            
        $(".pagination li").slice(1, -1).remove();
        getPageList(totalPages, currentPage, paginationSize).forEach( item => {
            $("<li>").addClass("page-item")
                     .addClass(item ? "current-page" : "disabled")
                     .toggleClass("active", item === currentPage).append(
                $("<a>").addClass("page-link").attr({
                    href: "javascript:void(0)"}).text(item || "...")
            ).insertBefore("#next-page");
        });
        // Disable prev/next when at first/last page:
        $("#previous-page").toggleClass("disabled", currentPage === 1);
        $("#next-page").toggleClass("disabled", currentPage === totalPages);
        return true;
    }

    // Include the prev/next buttons:
    $(".pagination").append(
        $("<li>").addClass("page-item").attr({ id: "previous-page" }).append(
            $("<a>").addClass("page-link").attr({
                href: "javascript:void(0)"}).text("Prev")
        ),
        $("<li>").addClass("page-item").attr({ id: "next-page" }).append(
            $("<a>").addClass("page-link").attr({
                href: "javascript:void(0)"}).text("Next")
        )
    );
    // Show the page links
    $("#jar").show();
    showPage(1);

    // Use event delegation, as these items are recreated later    
    $(document).on("click", ".pagination li.current-page:not(.active)", function () {
        return showPage(+$(this).text());
    });
    $("#next-page").on("click", function () {
        return showPage(currentPage+1);
    });

    $("#previous-page").on("click", function () {
        return showPage(currentPage-1);
    });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet">

<div class="pagination">
</div>

<div id="jar" style="display:none">
    <div class="content">1) Lorem ipsum dolor sit amet, consectetur adipiscing elit.</div>
    <div class="content">2) Maecenas vitae elit arcu.</div>
    <div class="content">3) Pellentesque sagittis risus ac ante ultricies, ac convallis urna elementum.</div>
    <div class="content">4) Vivamus sodales aliquam massa quis lobortis. </div>
    <div class="content">5) Phasellus id sem sollicitudin lacus condimentum malesuada vel tincidunt neque.</div>
    <div class="content">6) Donec magna leo, rhoncus quis nunc eu, malesuada consectetur orci.</div>
    <div class="content">7) Praesent sollicitudin, quam a ullamcorper pharetra, urna lacus mollis sem, quis semper augue massa ac est.</div>
    <div class="content">8) Etiam leo magna, fermentum quis quam non, aliquam tincidunt erat.</div>
    <div class="content">9) Morbi pellentesque nibh nec nibh posuere, vel tempor magna dignissim.</div>
    <div class="content">10) In maximus fermentum elementum. Vestibulum ac lectus pretium, suscipit ante nec, bibendum erat.</div>
    <div class="content">11) Phasellus sit amet orci at lectus fermentum congue. Etiam faucibus scelerisque purus.</div>
    <div class="content">12) Pellentesque laoreet ipsum ac laoreet consectetur. </div>
    <div class="content">13) Integer aliquet odio magna, lobortis mattis tortor suscipit sed.</div>
    <div class="content">14) Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. </div>
    <div class="content">15) Mauris a tellus luctus turpis elementum imperdiet vitae malesuada mauris. </div>
    <div class="content">16) Donec id libero sagittis, laoreet lorem vel, tempus nunc. </div>
    <div class="content">17) Donec vitae neque sed ex tristique hendrerit.</div>
    <div class="content">18) Aliquam sollicitudin gravida varius.</div>
    <div class="content">19) Donec auctor, augue sed finibus fermentum, neque erat interdum libero, eget porta metus lectus quis odio.</div>
    <div class="content">20) Nunc quis ante enim. Etiam nisl orci, hendrerit ut pretium nec, tempor in metus.</div>
    <div class="content">21) Donec et semper arcu.</div>
    <div class="content">22) Donec lobortis interdum purus, eu semper nisl pulvinar ac.</div>
    <div class="content">23) Cras laoreet eu elit vel porta.</div>
    <div class="content">24) Quisque pharetra arcu eget diam posuere commodo.</div>
    <div class="content">25) Nulla ornare eleifend neque, eget tincidunt nunc ullamcorper id. Nulla facilisi.</div>
</div>