ボタンが適用されているため、float-right
流れの一部が作成されます。参考:https ://www.w3.org/TR/CSS21/visuren.html#x23
追加するだけ
<div style="clear: both;"></div>
後に<button>
.container {
border: 1px solid black;
}
<!DOCTYPE html>
<html>
<head>
<link data-require="bootstrap@4.0.0-beta" data-semver="4.0.0-beta" rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/css/bootstrap.min.css" />
<script data-require="bootstrap@4.0.0-beta" data-semver="4.0.0-beta" src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="style.css" />
<script src="script.js"></script>
</head>
<body>
<div class="container">
<p>
Measured fer yer chains piracy marooned schooner snow yo-ho-ho parley furl six pounders lanyard. Snow brig Sink me rum American Main reef sails bucko pirate crow's nest Sail ho. American Main coxswain lee heave down tender brig schooner gibbet piracy rum.
</p>
<button type="button" class="btn btn-primary float-right">Primary</button>
<div style="clear: both;"></div>
</div>
</body>
</html>
方法 2 :
overflow: hidden;
に追加container
/* Styles go here */
.container {
border: 1px solid black;
overflow: hidden;
}
<!DOCTYPE html>
<html>
<head>
<link data-require="bootstrap@4.0.0-beta" data-semver="4.0.0-beta" rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/css/bootstrap.min.css" />
<script data-require="bootstrap@4.0.0-beta" data-semver="4.0.0-beta" src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="style.css" />
<script src="script.js"></script>
</head>
<body>
<div class="container">
<p>
Measured fer yer chains piracy marooned schooner snow yo-ho-ho parley furl six pounders lanyard. Snow brig Sink me rum American Main reef sails bucko pirate crow's nest Sail ho. American Main coxswain lee heave down tender brig schooner gibbet piracy rum.
</p>
<button type="button" class="btn btn-primary float-right">Primary</button>
</div>
</body>
</html>