var cols = $(".container .item").length;
if (cols == 5){
    $('div.item').removeClass('col-md-2..etc').addClass('col-md-3').css('width', '20%');
 }

Jquery和完成!框架!

用于引导4

Bootstrap 4现在默认使用flexbox，所以你可以直接使用它的神奇力量。查看自动布局列，根据嵌套的列的数量动态调整宽度。

这里有一个例子:

<div class="row">
   <div class="col">
      1 of 5
   </div>
   <div class="col">
      2 of 5
   </div>
   <div class="col">
      3 of 5
   </div>
   <div class="col">
      4 of 5
   </div>
   <div class="col">
      5 of 5
   </div>
</div>

演示工作

引导3

一个奇妙的全宽5列布局与Twitter引导创建在这里。

这是迄今为止最先进的解决方案，因为它与Bootstrap 3无缝地工作。它允许您一遍又一遍地重用这些类，并与当前的Bootstrap类一起用于响应式设计。

CSS: 将其添加到全局样式表中，甚至添加到bootstrap.css文档的底部。

.col-xs-5ths,
.col-sm-5ths,
.col-md-5ths,
.col-lg-5ths {
    position: relative;
    min-height: 1px;
    padding-right: 15px;
    padding-left: 15px;
}

.col-xs-5ths {
    width: 20%;
    float: left;
}

@media (min-width: 768px) {
    .col-sm-5ths {
        width: 20%;
        float: left;
    }
}

@media (min-width: 992px) {
    .col-md-5ths {
        width: 20%;
        float: left;
    }
}

@media (min-width: 1200px) {
    .col-lg-5ths {
        width: 20%;
        float: left;
    }
}

好好利用它!例如，如果你想创建一个div元素，它在中等屏幕上表现为五列布局，而在较小的屏幕上表现为两列布局，你只需要使用这样的东西:

<div class="row">
    <div class="col-md-5ths col-xs-6">
       ...
    </div>
</div>

工作演示-展开框架，看看列变得有响应。

另一个演示-将新的col-*-5ths类与其他类合并，如col-*-3和col-*-2。调整帧的大小，在响应视图中看到它们都改变为col-xs-6。

在bootstrap v4.3.1中，它是一个12 / 5 = 2.4列宽的列。我们称它为col-2dot4(以及col-sm-2dot4, col-md-2dot4，…)

每一列应该有20%的可用空间。

SCSS代码如下所示:

@mixin make-5-grid-column($columns: $grid-columns, $gutter: $grid-gutter-width, $breakpoints: $grid-breakpoints) {

  // Common properties for all breakpoints
  %grid-column {
    position: relative;
    width: 100%;
    padding-right: $gutter / 2;
    padding-left: $gutter / 2;
  }

  @each $breakpoint in map-keys($breakpoints) {
    $infix: breakpoint-infix($breakpoint, $breakpoints);

    .col#{$infix}-2dot4 {
      @extend %grid-column;
    }

    .col#{$infix},
    .col#{$infix}-auto {
      @extend %grid-column;
    }

    @include media-breakpoint-up($breakpoint, $breakpoints) {

      // Provide basic `.col-{bp}` classes for equal-width flexbox columns
      .col#{$infix} {
        flex-basis: 0;
        flex-grow: 1;
        max-width: 100%;
      }

      .col#{$infix}-auto {
        flex: 0 0 auto;
        width: auto;
        max-width: 100%; // Reset earlier grid tiers
      }


      .col#{$infix}-2dot4 {
        @include make-col(1, 5);
      }
    }
  }
}

@if $enable-grid-classes {
  @include make-5-grid-column();
}

我已经为任意数量的列创建了基于bootstrap定义的SASS mixin定义(个人而言，除了12列，我使用8、10和24列):

// Extended bootstrap grid system
//
// Framework grid generation
//
// Based on Bootstrap 'bootstrap/_grid-framework.scss'. Generates classes in form of `.col-(size)-x-num` of width x/num.

@mixin make-extended-grid-columns($num-columns, $i: 1, $list: ".col-xs-#{$i}-#{$num-columns}, .col-sm-#{$i}-#{$num-columns}, .col-md-#{$i}-#{$num-columns}, .col-lg-#{$i}-#{$num-columns}") {
    @for $i from (1 + 1) through $num-columns {
        $list: "#{$list}, .col-xs-#{$i}-#{$num-columns}, .col-sm-#{$i}-#{$num-columns}, .col-md-#{$i}-#{$num-columns}, .col-lg-#{$i}-#{$num-columns}";
    }
    #{$list} {
        position: relative;
        min-height: 1px;
        padding-left:  ($grid-gutter-width / 2);
        padding-right: ($grid-gutter-width / 2);
    }
}


@mixin float-extended-grid-columns($class, $num-columns, $i: 1, $list: ".col-#{$class}-#{$i}-#{$num-columns}") {
    @for $i from (1 + 1) through $num-columns {
        $list: "#{$list}, .col-#{$class}-#{$i}-#{$num-columns}";
    }
    #{$list} {
        float: left;
    }
}


@mixin calc-extended-grid-column($index, $num-columns, $class, $type) {
    @if ($type == width) and ($index > 0) {
        .col-#{$class}-#{$index}-#{$num-columns} {
            width: percentage(($index / $num-columns));
        }
    }
    @if ($type == push) and ($index > 0) {
        .col-#{$class}-push-#{$index}-#{$num-columns} {
            left: percentage(($index / $num-columns));
        }
    }
    @if ($type == pull) and ($index > 0) {
        .col-#{$class}-pull-#{$index}-#{$num-columns} {
            right: percentage(($index / $num-columns));
        }
    }
    @if ($type == offset) and ($index > 0) {
        .col-#{$class}-offset-#{$index}-#{$num-columns} {
            margin-left: percentage(($index / $num-columns));
        }
    }
}

@mixin loop-extended-grid-columns($num-columns, $class, $type) {
    @for $i from 1 through $num-columns - 1 {
        @include calc-extended-grid-column($i, $num-columns, $class, $type);
    }
}

@mixin make-extended-grid($class, $num-columns) {
    @include float-extended-grid-columns($class, $num-columns);
    @include loop-extended-grid-columns($num-columns, $class, width);
    @include loop-extended-grid-columns($num-columns, $class, pull);
    @include loop-extended-grid-columns($num-columns, $class, push);
    @include loop-extended-grid-columns($num-columns, $class, offset);
}

你可以简单地创建类:

$possible-number-extended-grid-columns: 8, 10, 24;

@each $num-columns in $possible-number-extended-grid-columns {

  // Columns

  @include make-extended-grid-columns($num-columns);

  // Extra small grid

  @include make-extended-grid(xs, $num-columns);

  // Small grid

  @media (min-width: $screen-sm-min) {
    @include make-extended-grid(sm, $num-columns);
  }

  // Medium grid

  @media (min-width: $screen-md-min) {
    @include make-extended-grid(md, $num-columns);
  }

  // Large grid

  @media (min-width: $screen-lg-min) {
    @include make-extended-grid(lg, $num-columns);
  }

}

我希望有人会觉得它有用

对于twitter bootstrap 3，这是最简单的方法来实现这一点:

<section class="col col-sm-3" style="width: 20%;">
<section class="col col-sm-3" style="width: 20%;">
<section class="col col-sm-3" style="width: 20%;">
<section class="col col-sm-3" style="width: 20%;">
<section class="col col-sm-3" style="width: 20%;">

Bootstrap默认可以缩放到12列?这意味着如果我们想要创建一个宽度相同的12列布局，我们将在div class="col-md-1"中写入12次。

<div class="row">
<div class="col-md-1"></div>    
<div class="col-md-2">1</div>
<div class="col-md-2">2</div>
<div class="col-md-2">3</div>
<div class="col-md-2">4</div>
<div class="col-md-2">5</div>
<div class="col-md-1"></div>
</div>