Css 表列大小

Updated 2018

Make sure your table includes the table class. This is because Bootstrap 4 tables are "opt-in" so the table class must be intentionally added to the table.

http://codeply.com/go/zJLXypKZxL

Bootstrap 3.x also had some CSS to reset the table cells so that they don't float..

table td[class*=col-], table th[class*=col-] {
    position: static;
    display: table-cell;
    float: none;
}

I don't know why this isn't is Bootstrap 4 alpha, but it may be added back in the final release. Adding this CSS will help all columns to use the widths set in the thead..

Bootstrap 4 Alpha 2 Demo

UPDATE (as of Bootstrap 4.0.0)

Now that Bootstrap 4 is flexbox, the table cells will not assume the correct width when adding col-*. A workaround is to use the d-inline-block class on the table cells to prevent the default display:flex of columns.

Another option in BS4 is to use the sizing utils classes for width...

<thead>
     <tr>
           <th class="w-25">25</th>
           <th class="w-50">50</th>
           <th class="w-25">25</th>
     </tr>
</thead>

Bootstrap 4 Alpha 6 Demo

Lastly, you could use d-flex on the table rows (tr), and the col-* grid classes on the columns (th,td)...

<table class="table table-bordered">
        <thead>
            <tr class="d-flex">
                <th class="col-3">25%</th>
                <th class="col-3">25%</th>
                <th class="col-6">50%</th>
            </tr>
        </thead>
        <tbody>
            <tr class="d-flex">
                <td class="col-sm-3">..</td>
                <td class="col-sm-3">..</td>
                <td class="col-sm-6">..</td>
            </tr>
        </tbody>
    </table>

Bootstrap 4.0.0 (stable) Demo

Note: Changing the TR to display:flex can alter the borders