正如@makshh在评论中提到的，现在似乎不可能做到这一点。我找到的唯一方法是来自@tsdexter的another stack overflow question：

$(document).ready(function(){
  $('.somecontainer').on('resize',function(){
    if ($('.somecontainer').width() < 640) {
        $('.somecontainer').addClass('m');
    } else {
        $('.somecontainer').removeClass('m');
    }
  });
});

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我只是设法让一个模态act中的网格系统响应Bootstrap 4中的模态断点。由于模态的max-width本身在某些断点上响应，我们需要在这些断点上为特定的模态大小（sm，md，lg，xl）生成新的css，这只是否决了Bootstrap的css媒体查询
只需将所有内容复制/粘贴到一个单独的scss文件中，激活它，就可以开始了

// This is a stripped version of the original "make-grid-columns" mixin from Bootstrap
@mixin make-modal-grid-columns($breakpoints) {
    @each $breakpoint in map-keys($breakpoints) {
        $infix: breakpoint-infix($breakpoint, $breakpoints);
        @include media-breakpoint-up($breakpoint, $breakpoints) {
            @for $i from 1 through $grid-columns {
                .col#{$infix}-#{$i} {
                    @include make-col($i, $grid-columns);
                }
            }
        }
    }
}

$breakpoint-sm: 576px;
$breakpoint-lg: 992px;
$breakpoint-xl: 1200px;

.modal {
    // Overrules all .col css inside .modal-sm to a single col
    .modal-sm {
        @include make-modal-grid-columns((
            xs: 0
        ));
    }

    // modal-md (no specific class is also modal-md)
    @include make-modal-grid-columns((
        sm: $breakpoint-sm
    ));

    .modal-lg {
         @include make-modal-grid-columns((
             md: $breakpoint-lg
         ));
     }

    .modal-xl {
        @include make-modal-grid-columns((
            md: $breakpoint-lg,
            lg: $breakpoint-xl
        ));
    }
}

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仅供参考：它生成350行代码