Bootstrap 4 - Flex
Descrizione
L'utilità Flex può essere utilizzata per gestire il layout, l'allineamento, le colonne della griglia, la navigazione e altri componenti della pagina. Rende facile progettare la struttura del layout senza utilizzare float o posizionamento.
Comportamenti e direzione flessibili
Utilizza le utilità di visualizzazione flexbox come d-flex e d-inline-flex per visualizzare il contenitore flexbox e gli elementi figli in elementi flessibili. Puoi impostare la direzione degli elementi flessibili in direzione orizzontale e verticale utilizzando .flex-row (usa .flex-row-reverse per visualizzare la direzione orizzontale dal lato opposto) e .flex-column (usa .flex-column-reverse per visualizzare la direzione verticale dal lato opposto) rispettivamente come mostrato nell'esempio seguente -
Esempio
<html>
<head>
<!-- Meta tags -->
<meta charset = "utf-8">
<meta name = "viewport" content = "width = device-width, initial-scale = 1, shrink-to-fit = no">
<!-- Bootstrap CSS -->
<link rel = "stylesheet"
href = "https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<title>Bootstrap 4 Example</title>
</head>
<body>
<div class = "container">
<h2>Flex Behaviors</h2>
<div class = "d-flex p-2 bg-info">
This is flex container, uses the 'd-flex' class
</div>
<br>
<div class = "d-inline-flex p-2 bg-info">
This is inline flexbox container, uses the 'd-inline-flex' class
</div>
<br>
<br>
<h2>Direction</h2>
<h4>Horizontal Direction</h4>
<div class = "d-flex flex-row bg-info mb-3">
<div class = "p-2 border border-dark ">flex-row: Item 1</div>
<div class = "p-2 border border-dark">flex-row: Item 2</div>
<div class = "p-2 border border-dark">flex-row: Item 3</div>
</div>
<div class = "d-flex flex-row-reverse bg-info">
<div class = "p-2 border border-dark">flex-row-reverse: Item 1</div>
<div class = "p-2 border border-dark">flex-row-reverse: Item 2</div>
<div class = "p-2 border border-dark">flex-row-reverse: Item 3</div>
</div>
<br>
<h4>Vertical Direction</h4>
<div class = "d-flex flex-column bg-info mb-3">
<div class = "p-2 border border-dark">flex-column: Item 1</div>
<div class = "p-2 border border-dark">flex-column: Item 2</div>
<div class = "p-2 border border-dark">flex-column: Item 3</div>
</div>
<div class = "d-flex flex-column-reverse bg-info">
<div class = "p-2 border border-dark">flex-column-reverse: Item 1</div>
<div class = "p-2 border border-dark">flex-column-reverse: Item 2</div>
<div class = "p-2 border border-dark">flex-column-reverse: Item 3</div>
</div>
</div>
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src = "https://code.jquery.com/jquery-3.2.1.slim.min.js"
integrity = "sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN"
crossorigin = "anonymous">
</script>
<!-- Popper -->
<script src = "https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"
integrity = "sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q"
crossorigin = "anonymous">
</script>
<!-- Latest compiled and minified Bootstrap JavaScript -->
<script src = "https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"
integrity = "sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl"
crossorigin = "anonymous">
</script>
</body>
</html>Produrrà il seguente risultato:
Produzione
Giustifica il contenuto
L'allineamento degli elementi flessibili (come inizio, fine, centro, tra e intorno) può essere modificato sull'asse principale (asse x all'inizio) dei contenitori flexbox utilizzando l' utilità justify-content .
Il seguente esempio lo dimostra:
Esempio
<html>
<head>
<!-- Meta tags -->
<meta charset = "utf-8">
<meta name = "viewport" content = "width = device-width, initial-scale = 1, shrink-to-fit = no">
<!-- Bootstrap CSS -->
<link rel = "stylesheet"
href = "https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<title>Bootstrap 4 Example</title>
</head>
<body>
<div class = "container">
<h2>Alignment - Start</h2>
<div class = "d-flex justify-content-start bg-info">
<div class = "p-2 border border-dark">Item 1</div>
<div class = "p-2 border border-dark">Item 2</div>
<div class = "p-2 border border-dark">Item 3</div>
</div>
<br>
<h2>Alignment - End</h2>
<div class = "d-flex justify-content-end bg-info">
<div class = "p-2 border border-dark">Item 1</div>
<div class = "p-2 border border-dark">Item 2</div>
<div class = "p-2 border border-dark">Item 3</div>
</div>
<br>
<h2>Alignment - Center</h2>
<div class = "d-flex justify-content-center bg-info">
<div class = "p-2 border border-dark">Item 1</div>
<div class = "p-2 border border-dark">Item 2</div>
<div class = "p-2 border border-dark">Item 3</div>
</div>
<br>
<h2>Alignment - Between</h2>
<div class = "d-flex justify-content-between bg-info">
<div class = "p-2 border border-dark">Item 1</div>
<div class = "p-2 border border-dark">Item 2</div>
<div class = "p-2 border border-dark">Item 3</div>
</div>
<br>
<h2>Alignment - Around</h2>
<div class = "d-flex justify-content-around bg-info">
<div class = "p-2 border border-dark">Item 1</div>
<div class = "p-2 border border-dark">Item 2</div>
<div class = "p-2 border border-dark">Item 3</div>
</div>
</div>
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src = "https://code.jquery.com/jquery-3.2.1.slim.min.js"
integrity = "sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN"
crossorigin = "anonymous">
</script>
<!-- Popper -->
<script src = "https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"
integrity = "sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q"
crossorigin = "anonymous">
</script>
<!-- Latest compiled and minified Bootstrap JavaScript -->
<script src = "https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"
integrity = "sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl"
crossorigin = "anonymous">
</script>
</body>
</html>Produrrà il seguente risultato:
Produzione
Allinea elementi
L'allineamento degli elementi flessibili (come inizio, fine, centro, linea di base e allungamento) può essere modificato sull'asse trasversale (asse y all'inizio) dei contenitori flexbox utilizzando l' utilità align-items .
Il seguente esempio lo dimostra:
Esempio
<html>
<head>
<!-- Meta tags -->
<meta charset = "utf-8">
<meta name = "viewport" content = "width = device-width, initial-scale = 1, shrink-to-fit = no">
<!-- Bootstrap CSS -->
<link rel = "stylesheet"
href = "https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<title>Bootstrap 4 Example</title>
</head>
<body>
<div class = "container">
<h2>Align Items - Start</h2>
<div class = "d-flex align-items-start bg-info" style = "height: 100px">
<div class = "p-2 border border-dark">Item 1</div>
<div class = "p-2 border border-dark">Item 2</div>
<div class = "p-2 border border-dark">Item 3</div>
</div>
<br>
<h2>Align Items - End</h2>
<div class = "d-flex align-items-end bg-info" style = "height: 100px">
<div class = "p-2 border border-dark">Item 1</div>
<div class = "p-2 border border-dark">Item 2</div>
<div class = "p-2 border border-dark">Item 3</div>
</div>
<br>
<h2>Align Items - Center</h2>
<div class = "d-flex align-items-center bg-info" style = "height: 100px">
<div class = "p-2 border border-dark">Item 1</div>
<div class = "p-2 border border-dark">Item 2</div>
<div class = "p-2 border border-dark">Item 3</div>
</div>
<br>
<h2>Align Items - Baseline</h2>
<div class = "d-flex align-items-baseline bg-info" style = "height: 100px">
<div class = "p-2 border border-dark">Item 1</div>
<div class = "p-2 border border-dark">Item 2</div>
<div class = "p-2 border border-dark">Item 3</div>
</div>
<br>
<h2>Align Items - Stretch</h2>
<div class = "d-flex align-items-stretch bg-info" style = "height: 100px">
<div class = "p-2 border border-dark">Item 1</div>
<div class = "p-2 border border-dark">Item 2</div>
<div class = "p-2 border border-dark">Item 3</div>
</div>
<br>
</div>
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src = "https://code.jquery.com/jquery-3.2.1.slim.min.js"
integrity = "sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN"
crossorigin = "anonymous">
</script>
<!-- Popper -->
<script src = "https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"
integrity = "sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q"
crossorigin = "anonymous">
</script>
<!-- Latest compiled and minified Bootstrap JavaScript -->
<script src = "https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"
integrity = "sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl"
crossorigin = "anonymous">
</script>
</body>
</html>Produrrà il seguente risultato:
Produzione
Riempi, ingrandisci e rimpicciolisci
Gli elementi possono essere visualizzati in larghezze uguali sullo spazio orizzontale utilizzando la classe .flex-fill . L'elemento flex crescerà, se c'è spazio disponibile usando .flex-grow- * class e l'elemento flex si restringerà, se necessario usando .flex-shrink- * class.
Il seguente esempio dimostra l'utilizzo delle utilità di cui sopra:
Esempio
<html>
<head>
<!-- Meta tags -->
<meta charset = "utf-8">
<meta name = "viewport" content = "width = device-width, initial-scale = 1, shrink-to-fit = no">
<!-- Bootstrap CSS -->
<link rel = "stylesheet"
href = "https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<title>Bootstrap 4 Example</title>
</head>
<body>
<div class = "container">
<h2>Fill</h2>
<div class = "d-flex bg-info">
<div class = "p-2 flex-fill border border-dark">Item 1</div>
<div class = "p-2 flex-fill border border-dark">Item 2</div>
<div class = "p-2 flex-fill border border-dark">Item 3</div>
</div>
<br>
<h2>Grow</h2>
<div class = "d-flex bg-info">
<div class = "p-2 flex-grow-1 bg-info">Item 1 (Using class flex-grow-1)</div>
<div class = "p-2 bg-warning">Item 2</div>
<div class = "p-2 bg-secondary">Item 3</div>
</div>
<br>
<h2>Shrink</h2>
<div class = "d-flex bg-info">
<div class = "p-2 w-100 bg-info">Item 1</div>
<div class = "p-2 flex-shrink-1 bg-warning">Item 2 (Using class flex-shrink-1)</div>
</div>
</div>
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src = "https://code.jquery.com/jquery-3.2.1.slim.min.js"
integrity = "sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN"
crossorigin = "anonymous">
</script>
<!-- Popper -->
<script src = "https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"
integrity = "sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q"
crossorigin = "anonymous">
</script>
<!-- Latest compiled and minified Bootstrap JavaScript -->
<script src = "https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"
integrity = "sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl"
crossorigin = "anonymous">
</script>
</body>
</html>Produrrà il seguente risultato:
Produzione
Margini automatici e con elementi di allineamento
L'utility flex fornisce la funzione di margine automatico sugli elementi flex utilizzando le classi .mr-auto (spinge gli elementi a destra) e .ml-auto (spinge gli elementi a sinistra). Gli elementi flessibili possono essere spostati in alto o in basso utilizzando le classi mt-auto o mb-auto su un contenitore.
Il seguente esempio dimostra l'utilizzo delle classi precedenti:
Esempio
<html>
<head>
<!-- Meta tags -->
<meta charset = "utf-8">
<meta name = "viewport" content = "width = device-width, initial-scale = 1, shrink-to-fit = no">
<!-- Bootstrap CSS -->
<link rel = "stylesheet"
href = "https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<title>Bootstrap 4 Example</title>
</head>
<body>
<div class = "container">
<h2>Auto Margins</h2>
<div class = "d-flex bg-info mb-3">
<div class = "p-2 bg-warning">Item 1</div>
<div class = "p-2 bg-primary">Item 2</div>
<div class = "p-2 bg-secondary">Item 3</div>
</div>
<div class = "d-flex bg-info mb-3">
<div class = "mr-auto p-2 bg-warning">mr-auto: Item 1</div>
<div class = "p-2 bg-primary">Item 2</div>
<div class = "p-2 bg-secondary">Item 3</div>
</div>
<div class = "d-flex bg-info mb-3">
<div class = "p-2 bg-secondary">Item 1</div>
<div class = "p-2 bg-primary">Item 2</div>
<div class = "ml-auto p-2 bg-warning">ml-auto: Item 3</div>
</div>
<h2>With align-items</h2>
<div class = "d-flex align-items-start flex-column bg-info mb-3"
style = "height: 200px;">
<div class = "mb-auto p-2 bg-warning">mb-auto: Item 1</div>
<div class = "p-2 bg-primary">Item 2</div>
<div class = "p-2 bg-secondary">Item 3</div>
</div>
<div class = "d-flex align-items-end flex-column bg-info mb-3"
style = "height: 200px;">
<div class = "p-2 bg-secondary">Item 1</div>
<div class = "p-2 bg-primary">Item 2</div>
<div class = "mt-auto p-2 bg-warning">mt-auto: Item 3</div>
</div>
</div>
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src = "https://code.jquery.com/jquery-3.2.1.slim.min.js"
integrity = "sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN"
crossorigin = "anonymous">
</script>
<!-- Popper -->
<script src = "https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"
integrity = "sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q"
crossorigin = "anonymous">
</script>
<!-- Latest compiled and minified Bootstrap JavaScript -->
<script src = "https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"
integrity = "sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl"
crossorigin = "anonymous">
</script>
</body>
</html>Produrrà il seguente risultato:
Produzione
Ordine
Flex utilizza le utilità di ordine per modificare l'ordine degli elementi flessibili in un contenitore come mostrato nell'esempio seguente:
Esempio
<html>
<head>
<!-- Meta tags -->
<meta charset = "utf-8">
<meta name = "viewport" content = "width = device-width, initial-scale = 1, shrink-to-fit = no">
<!-- Bootstrap CSS -->
<link rel = "stylesheet"
href = "https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<title>Bootstrap 4 Example</title>
</head>
<body>
<div class = "container">
<h2>Flex Items Order</h2>
<div class = "d-flex flex-nowrap bg-info">
<div class = "order-3 p-2 bg-secondary">'order-3': Item 1</div>
<div class = "order-1 p-2 bg-primary">'order-1': Item 2</div>
<div class = "order-2 p-2 bg-warning">'order-2': Item 3</div>
</div>
</div>
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src = "https://code.jquery.com/jquery-3.2.1.slim.min.js"
integrity = "sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN"
crossorigin = "anonymous">
</script>
<!-- Popper -->
<script src = "https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"
integrity = "sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q"
crossorigin = "anonymous">
</script>
<!-- Latest compiled and minified Bootstrap JavaScript -->
<script src = "https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"
integrity = "sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl"
crossorigin = "anonymous">
</script>
</body>
</html>Produrrà il seguente risultato:
Produzione
Allinea contenuto
È possibile allineare (come inizio, fine, centro, tra e intorno) gli elementi flessibili sull'asse trasversale del contenitore utilizzando l' utilità di allineamento del contenuto .
Il seguente esempio lo dimostra:
Esempio
<html>
<head>
<!-- Meta tags -->
<meta charset="utf-8">
<meta name = "viewport" content = "width = device-width, initial-scale = 1, shrink-to-fit = no">
<!-- Bootstrap CSS -->
<link rel = "stylesheet"
href = "https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<title>Bootstrap 4 Example</title>
</head>
<body>
<div class = "container">
<h2>align-content-start</h2>
<div class = "d-flex bg-info align-content-start flex-wrap" style = "height: 150px">
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
</div>
<br>
<h2>align-content-end</h2>
<div class = "d-flex bg-info align-content-end flex-wrap" style = "height: 150px">
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
</div>
<br>
<h2>align-content-center</h2>
<div class = "d-flex bg-info align-content-center flex-wrap" style = "height: 150px">
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
</div>
<br>
<h2>align-content-between</h2>
<div class = "d-flex bg-info align-content-between flex-wrap" style = "height: 150px">
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
</div>
<br>
<h2>align-content-around</h2>
<div class = "d-flex bg-info align-content-around flex-wrap" style = "height: 150px">
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
<div class = "p-2 border border-dark">Demo Item</div>
</div>
<br>
</div>
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src = "https://code.jquery.com/jquery-3.2.1.slim.min.js"
integrity = "sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN"
crossorigin = "anonymous">
</script>
<!-- Popper -->
<script src = "https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"
integrity = "sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q"
crossorigin = "anonymous">
</script>
<!-- Latest compiled and minified Bootstrap JavaScript -->
<script src = "https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"
integrity = "sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl"
crossorigin = "anonymous">
</script>
</body>
</html>Produrrà il seguente risultato: