如何檢查第一個/最後一個元素是否具有特定的類？

Question

我正在做一個標籤導航，並遇到麻煩。 如果活動標籤是第一個，我想禁用上一個按鈕，如果最後一個標籤處於活動狀態，則禁用下一個按鈕。

我如何檢查的第一個/最後一個標籤是活躍在這裏？

$(document).ready(function() { 
 

 
    $('ul.tabs li').click(function() { 
 
    var tab_id = $(this).attr('data-tab'); 
 

 
    $('ul.tabs li').removeClass('current'); 
 
    $('.tab-content').removeClass('current'); 
 

 
    $(this).addClass('current'); 
 
    $("#" + tab_id).addClass('current'); 
 
    }) 
 

 
    $('#previous').click(function() { 
 
    if($('ul.tabs li.current').prev().length != 0){ 
 
    $('ul.tabs li.current').removeClass('current').prev().addClass('current').click(); 
 
} 
 
    }) 
 

 
    $('#next').click(function() { 
 
\t if($('ul.tabs li.current').next().length != 0){ 
 
    $('ul.tabs li.current').removeClass('current').next().addClass('current').click(); 
 
\t \t } 
 
    }); 
 
})

body { 
 
    margin-top: 100px; 
 
    font-family: 'Trebuchet MS', serif; 
 
    line-height: 1.6 
 
} 
 

 
.container { 
 
    width: 800px; 
 
    margin: 0 auto; 
 
} 
 

 
ul.tabs { 
 
    margin: 0px; 
 
    padding: 0px; 
 
    list-style: none; 
 
} 
 

 
ul.tabs li { 
 
    background: none; 
 
    color: #222; 
 
    display: inline-block; 
 
    padding: 10px 15px; 
 
    cursor: pointer; 
 
} 
 

 
ul.tabs li.current { 
 
    background: #ededed; 
 
    color: #222; 
 
} 
 

 
ul.arrownavigation { 
 
    list-style: none; 
 
} 
 

 
ul.arrownavigation li { 
 
    display: inline-block; 
 
    background: #111; 
 
    color: #fff; 
 
    padding: 10px; 
 
    cursor: pointer; 
 
} 
 

 
ul.arrownavigation li:active { 
 
    background: #444; 
 
} 
 

 
ul.arrownavigation li.disabled { 
 
    opacity: 0.7; 
 
} 
 

 
.tab-content { 
 
    display: none; 
 
    background: #ededed; 
 
    padding: 15px; 
 
} 
 

 
.tab-content.current { 
 
    display: inherit; 
 
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> 
 
<div class="container"> 
 

 
    <ul class="arrownavigation"> 
 
    <li id="previous">Previous</li> 
 
    <li id="next">Next</li> 
 
    </ul> 
 

 
    <ul class="tabs"> 
 
    <li class="tab-link current" data-tab="tab-1">Tab One</li> 
 
    <li class="tab-link" data-tab="tab-2">Tab Two</li> 
 
    <li class="tab-link" data-tab="tab-3">Tab Three</li> 
 
    <li class="tab-link" data-tab="tab-4">Tab Four</li> 
 
    </ul> 
 

 
    <div id="tab-1" class="tab-content current"> 
 
    Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. 
 
    </div> 
 
    <div id="tab-2" class="tab-content"> 
 
    Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. 
 
    </div> 
 
    <div id="tab-3" class="tab-content"> 
 
    Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. 
 
    </div> 
 
    <div id="tab-4" class="tab-content"> 
 
    Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. 
 
    </div> 
 

 
</div> 
 
<!-- container -->

Answer 1

你需要做的是檢查第一和最後一個選項卡有current類。稍微修改腳本（更普遍的，可重複使用的）如下：

$('.tabs-container').each(function(i) { 
 

 
    var tabsContainer = $(this); 
 
    var tabsNavigation = tabsContainer.find('.arrownavigation'); 
 
    var tabsLinks = tabsContainer.find('.tab-link'); 
 
    var tabLinkFirst = tabsContainer.find('.tab-link:first-child'); 
 
    var tabLinkLast = tabsContainer.find('.tab-link:last-child'); 
 
    var tabsContent = tabsContainer.find('.tab-content'); 
 
    var tabsPrevious = tabsContainer.find('.tab-previous'); 
 
    var tabsNext = tabsContainer.find('.tab-next'); 
 
    
 
    /* This is the function you need: */ 
 
    function checkArrows() { 
 
    \t tabsPrevious.toggleClass('tab-disabled', tabLinkFirst.hasClass('current')); 
 
     tabsNext.toggleClass('tab-disabled', tabLinkLast.hasClass('current')); 
 
    }; 
 
    checkArrows(); 
 

 
    tabsLinks.click(function() { 
 
     var tabSelector = $(this).data('tab'); 
 
     $('ul.tabs li').removeClass('current'); 
 
     $('.tab-content').removeClass('current'); 
 
     $(this).addClass('current'); 
 
     $(tabSelector).addClass('current'); 
 
     checkArrows(); 
 
    }); 
 

 
    tabsPrevious.click(function() { 
 
     var currentTab = tabsContainer.find('.tabs li.current'); 
 
     if (currentTab.prev().length > 0) { 
 
      currentTab.removeClass('current').prev().addClass('current').trigger('click'); 
 
     } 
 
    }); 
 

 
    tabsNext.click(function() { 
 
     var currentTab = tabsContainer.find('.tabs li.current'); 
 
     if (currentTab.next().length > 0) { 
 
      currentTab.removeClass('current').next().addClass('current').trigger('click'); 
 
     } 
 
    }); 
 

 
})

body { 
 
    margin-top: 100px; 
 
    font-family: 'Trebuchet MS', serif; 
 
    line-height: 1.6 
 
} 
 

 
.tabs-container { 
 
    width: 800px; 
 
    margin: 0 auto; 
 
} 
 

 
ul.tabs { 
 
    margin: 0px; 
 
    padding: 0px; 
 
    list-style: none; 
 
} 
 

 
ul.tabs li { 
 
    background: none; 
 
    color: #222; 
 
    display: inline-block; 
 
    padding: 10px 15px; 
 
    cursor: pointer; 
 
} 
 

 
ul.tabs li.current { 
 
    background: #ededed; 
 
    color: #222; 
 
} 
 

 
ul.arrownavigation { 
 
    list-style: none; 
 
} 
 

 
ul.arrownavigation li { 
 
    display: inline-block; 
 
    background: #111; 
 
    color: #fff; 
 
    padding: 10px; 
 
    cursor: pointer; 
 
} 
 

 
ul.arrownavigation li:active { 
 
    background: #444; 
 
} 
 

 
ul.arrownavigation li.disabled { 
 
    opacity: 0.7; 
 
} 
 

 
.tab-content { 
 
    display: none; 
 
    background: #ededed; 
 
    padding: 15px; 
 
} 
 

 
.tab-content.current { 
 
    display: inherit; 
 
} 
 

 
ul.arrownavigation li.tab-disabled { 
 
    background: none #ccc; 
 
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> 
 
<div class="tabs-container"> 
 

 
    <ul class="arrownavigation"> 
 
     <li class="tab-arrow tab-previous">Previous</li> 
 
     <li class="tab-arrow tab-next">Next</li> 
 
    </ul> 
 

 
    <ul class="tabs"> 
 
     <li class="tab-link current" data-tab=".tab-1">Tab One</li> 
 
     <li class="tab-link" data-tab=".tab-2">Tab Two</li> 
 
     <li class="tab-link" data-tab=".tab-3">Tab Three</li> 
 
     <li class="tab-link" data-tab=".tab-4">Tab Four</li> 
 
    </ul> 
 

 
    <div class="tab-content tab-1 current"> 
 
     Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. 
 
    </div> 
 
    <div class="tab-content tab-2"> 
 
     Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. 
 
    </div> 
 
    <div class="tab-content tab-3"> 
 
     Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. 
 
    </div> 
 
    <div class="tab-content tab-4"> 
 
     Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. 
 
    </div> 
 

 
</div>

同樣在JSFiddle。

Answer 2

你可以改變你的點擊功能這樣

$('ul.tabs li').click(function() { 
    var tab_id = $(this).attr('data-tab'); 
    var index = $(".tabs li").index(this); 

    if (index == 0) 
    { 
     $('#previous').hide(); 
    } 
    else if (index + 1 == $(".tabs li").length) 
    { 
     $('#next').hide(); 
    } 
    else 
    { 
     $('#next').show(); 
     $('#previous').show(); 
    } 

    $('ul.tabs li').removeClass('current'); 
    $('.tab-content').removeClass('current'); 

    $(this).addClass('current'); 
    $("#" + tab_id).addClass('current'); 
})