Top 20 Bootstrap Interview Questions & Answers 2022

Bootstrap is a mobile first front-end framework for easier web development with supporting all virtual devices. It uses HTML, CSS, JavaScript.
(1). Why should we use Bootstrap?
Every browser can support bootstrap features. With the knowledge of HTML, CSS, and JavaScript anyone can start working with Bootstrap. Bootstrap responsive CSS adjusts to Desktops, Mobiles, and Tablets. It provides web-based customization. Bootstrap is open source. It can be used for mobile first design styles using the entire library instead of separate and different files.
(2). What are Responsive websites?
Responsive means a website can be used on any platform with all types of screen size. A platform like it may be a desktop, laptop, tablet or smartphones. It automatically adjusts with changing the width and height of the screen.
In today’s era, people, as well as business, follow the smartphones for their personal and professional use. So, bootstrap is the best choice to make the website one time and it supports all kinds of devices.
(3). What are the features of Bootstrap v4?
The initial release of bootstrap v4.x was 4.0 and the final release in 2018-2019 is 4.2 ;
- The toast component is added for showing notifications
- The spinner component is added for loading
- The utility class .text-decoration-none is added
- The bootstrap-grid.css file updates the margin and padding of the grid system
- The .modal-xl class is used for modals
- The .font-weight-lighter and .font-weight-bolder are added as utility classes
- The validation styles for file inputs is added with new features
- The print feature of dark tables is updated with new quality
- The new utility class .dropdown-item-text is added for dropdown items
- The Tooltips supports Shadow DOM
- The double transitions issue on carousels is improved now
(4). What is a Source map file?
A source map file allows the web debuggers to refer to the original context from where the code was generated. The file has the .map extension.
(5). How to make images responsive using bootstrap3?
We can make responsive images using .img-responsive class. Let’s see the code,
```
<div class="container">
<img class="img-responsive" src="images/Satya.jpg" alt="Responsive"/><div>
```
(6). How to create responsive images in Bootstrap 4?
Bootstrap 4 works with .img-fluid to build responsive images. Let’s see the code,
```
<div class="container">
 <img src="/Satya/Pics/Name.jpg" class="img-fluid" alt="">
</div>
```

(7). How to make videos responsive in bootstrap3?

We can create responsive using a .embed-responsive class. Then we will add the .embed-responsive-item class to an <iframe> tag. Let’s see the code,

<div class="container">
<div class="embed-responsive">
<iframe class="embed-responsive-item"src="https://www.youtube.com/channel/UCrxtdnFenZ5aDVQmHv2iGGg/videos?view_as=subscriber&disable_polymer=1"></iframe>
</div>
</div>

(8). How to make tab component using bootstrap?
We can create nav components such as tabs using Twitter Bootstrap. You can use .nav-tabs class with the base class .nav.
```
<ul class="nav nav-tabs">
<li class="active"><a href="#">Profile</a></li>
<li><a href="#">Details</a></li>
<li><a href="#">Contact</a></li>
</ul>
```
(9). How many types of classes are used in Bootstrap3 to create a responsive page layout?
There are 4 types of bootstrap grid classes. we can create grid column layouts extra small devices like mobile phones to large devices like large desktop screens.
.col-xs-* : This class is used for extra small device like smart phone (Size<768px)
.col-sm-*: This class is used for small device like tablets (size>=768px)
.col-md-*: This class is used for medium device like laptops and small size desktop CRT screen (size >=992px)
.col-lg-* : This class is used for large device like flat screen or large size desktop (size>=1200px)
(10). How to hide elements in Bootstrap3 based on device?
This can be possible using hidden utility classes. See
hidden-sm-* : Hide the elements only on small devices
hidden-md-*: Hide the elements only on medium devi
hidden-lg-*: Hide the elements only on larger devices.
(11). How to visible elements based on device screen?
This can be possible using hidden utility classes. See the below classes,
visible-xs-*: Visible the elements only on extra small de
visible-sm-*: Visible the elements only on small devices.
visible-md-*: Visible the elements only on medium devi
1. visible-lg-*: Visible the elements only on larger devices.
2. (12). How to show certain elements for printing purpose?
  visible-print class is visible for printing purpose. Let’s see the code,
```
<div class="container">
<div class="row">
<div class="col-xs-10 visible-print">

</div>
</div>
</div>
```
3. (13). What is the grid size in Bootstrap 4?
  Bootstrap 4 supports 5 tier grid system. The below lists for different screen sizes of device,
  Extra small <576px :
  - Width container will be auto.
  - Here class prefix is .col-.
  - A number of columns will be 12.
  - It can be nestable.
  - It supports column ordering.
  Small =576px :
  - Width container will be 540px.
  - Here class prefix is .col-sm-.
  - A number of columns will be 12.
  - It can be nestable.
  - It supports column ordering.
  Medium =768px :
  - Width container will be 720px.
  - Here class prefix is .col-md-.
  - A number of columns will be 12.
  - It can be nestable.
  - It supports column ordering.
  Large =992px:
  - Width container will be 960px.
  - Here class prefix is .col-lg-.
  - A number of columns will be 12.
  - It can be nestable.
  - It supports column ordering.
  Extra large =1200px :
  - Width container will be 1140px.
  - Here class prefix is .col-xl-.
  - A number of columns will be 12.
  - It can be nestable.
  - It supports column ordering.
4. (14). How to create a bootstrap tooltip using jQuery?
  Using data-toggle attribute that means include data-toggle="tooltip" to the element and initialize it using jQuery. For setting the tooltip message include the title attribute to the element.
  Let’s see the code,
```
<button class="btn btn-primary" tooltip="The title message is shown"
data-toggle="tooltip">
 Click Here
</button>

<script type="text/javascript">
 $(document).ready(function () {
 $('[data-toggle="tooltip"]').tooltip();
 });
</script>
```
5. (15). How to set alert using JavaScript?
  To create an alert, I can use the alert class. Types of alert contextual classes are mentioned below,
  1. alert-danger: This can be used for error purpose.
  2. alert-success: This can be used for success purpose.
  3. alert-danger: This can be used for information purpose.
  4. alert-warning: This can be used for warning purpose.
  First, create a button element for click event and then create div element with ID and message information.
```
<button id="btnAlert" class="btn btn-primary">
 Alert
</button>

<div id="dvAlert" class="alert alert-danger collapse">
<a href="#" class="close" data-dismiss="alert">×</a>
<strong>Error!</strong> Check once using unit test.
</div>
 Next step is to mention div id inside button click event using jquery.
<script type="text/javascript">
 $(document).ready(function () {

 $('#btnAlert').click(function () {
 $('#dvAlert').show('fade');
 });

 });
</script>
```
6. (16). How to toggle a drop-down menu using JavaScript?
  Using .dropdown-toggle class of an anchor link or a button using JavaScript.
```
<button class="btn btn-primary dropdown-toggle" type="button" data-toggle="dropdown">
 Dropdown menu
<span class="caret"></span>
</button>
<script>
 $(document).ready(function () {
 $(".dropdown-toggle").dropdown();
 });
</script>
```
7. (17). What is the relationship between Sass and bootstrap?
  SASS is a stylesheet language and CSS pre-processors. It should be compiled into CSS and that can be understood by the Web browser. The files are written in SASS that have the. scss extension. The complete Bootstrap 4 CSS source is written in the SASS language.
  The Bootstrap 4 CSS files are compiled using a SASS compiler i.e. A.K.A pre-processor. SASS is the best way to way to customize Bootstrap.
8. (18). What is the difference between Bootstrap v3 and v4?
  Bootstrap 4 is the latest version of Bootstrap. It is the most popular framework including HTML, CSS, and JavaScript. New components are added in Bootstrap 4. The final release in 2018-2019 is 4.2:
  COMPONENTS
  BOOTSTRAP v3
  BOOTSTRAP v4
  font size
  The global font size is 14px
  The global font size is 16px
  primary CSS unit
  The primary CSS unit is px
  The primary CSS unit is rem
  source CSS files
  The source CSS files are named as LESS
  The source CSS files are named as SCSS
  grid system
  It has 4 tier grid system(These are xs, sm, md, lg)
  It has 5 tier grid system(These are xs, sm, md, lg, xl)
  offset columns
  It implements col-*-offset-* classes to offset columns
  It uses offset-*-* classes to offset columns
  inverse tables
  The inverse table is not supported
  Uses inverse tables by .table-dark
  condensed tables
  The .table-condensed is used for condensed tables
  The .table-sm is used for condensed tables
  contextual table classes
  It doesn't contain .table- prefix for its contextual classes
  It contains .table- prefix for its contextual classes
  radio buttons
  It uses .radio, .radio-inline to display radio buttons
  It uses .form-check-input, .form-check-inline to display checkboxes
  checkboxes
  It uses .checkbox, .checkbox-inline to display checkboxes
  It uses .form-check, .form-check-label to display radio buttons
  input controls size
  It uses .input-lg and .input-sm to customize the size of an input controls
  It uses form-control-lg and .form-control-sm to customize the size of an input controls
  label size
  It doesn't contain any classes for changing form label size
  It uses .col-form-label-sm and .col-form-label-lg to customize the size of a label
  help text
  It uses .help-block class to show help text
  It uses the .form-text class to show help text
  form legends
  It has no classes for making the form legends
  It uses .col-form-label on legend elements
  validation styles
  It contains validation styles for validating states on form controls(like .has-warning)
  It doesn't contain validation styles
  custom forms
  It doesn't support custom forms
  It supports custom forms
  buttons
  It contains .btn-default and .btn-info classes but .btn-secondary is not found
  It contains the .btn-secondary, .btn-light, and .btn-dark classes
  outline button
  It doesn't contain the outline button
  It supports .btn-outline-* classes for adding styles buttons using an outline colour
  button sizes
  It uses .btn-xs for button sizes
  The .btn-sm and .btn-lg are used but .btn-xs class is no longer available
  responsive images
  It uses .img-responsive class for responsive images
  It uses .img-fluid class for responsive images
  image alignment
  It uses .pull-right, .pull-left for right and left image alignment
  It uses .pull-*-right and .pull-*-left for right and left image alignment
  block level images
  It uses .center-block to align block level images
  It uses .m-x-auto to align block level images
  Dropdown header
  It uses li tags to build dropdowns with .dropdown-header
  It uses to h1 - h2 tags to build dropdowns with .dropdown-header
  Divider in dropdown
  It uses .divider class to the li element to make lists of build dropdowns
  It uses .divider class to the div element to make lists of build dropdowns
  disable menu items
  It uses the .disabled class to the li element to disable menu items
  It uses .disabled class to the <a> element to disable menu items
  Nav inline
  There is no .nav-inline class
  It uses the .nav-inline class for specifying navs to be displayed inline
  navbar alignment
  It uses .navbar-right, .navbar-left for navbar alignment
  It uses .mr-auto for navbar alignment
  Fixed navbar
  It uses .navbar-fixed-top and .navbar-fixed-bottom for setting navbar in top or bottom
  It uses .fixed-top and .fixed-bottom for setting navbar in top or bottom
  glyphicons
  It supports glyphicons
  It doesn’t support glyphicons
  carousel item
  It uses .item class for carousel item
  It uses .carousel-item class
  affix
  It supports affix
  It doesn’t support it
  Thumbnails
  It supports thumbnails
  It doesn’t support it
  Wells and Panels
  It supports both
  It doesn’t support it
  cards
  It doesn’t support it
  It supports cards instead of affix, thumbnails, wells and panels
9. (19). What are cards in Bootstrap 4?
  Bootstrap 4 uses cards by replacing panels, wells, and thumbnails. Bootstrap 4 uses .card and .card-body classes to an element to make container. It adds .card-title to heading elements and It uses .card-text to text elements.
  Let’ see code,
```
<div class="container-fluid">
 <div class="card card-body">
 <h4 class="card-title">Name</h4>
 <p class="card-text">My name is Satyaprakash</p>
 <a href="#" class="btn btn-primary">More Detilas>></a>
 </div>
</div>
```
Summary
I hope these questions and answers will help you to crack your Bootstrap Interview. These interview Questions have been taken from our new released eBook Bootstrap Interview Questions & Answers. This book contains more than 220 Bootstrap interview questions.

Thank you For Reading

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Top 20 Bootstrap Interview Questions & Answers 2022

Top 20 Bootstrap Interview Questions & Answers 2022

(1). Why should we use Bootstrap?

(2). What are Responsive websites?

(3). What are the features of Bootstrap v4?

(4). What is a Source map file?

(5). How to make images responsive using bootstrap3?

(6). How to create responsive images in Bootstrap 4?

(7). How to make videos responsive in bootstrap3?

(8). How to make tab component using bootstrap?

(9). How many types of classes are used in Bootstrap3 to create a responsive page layout?

(10). How to hide elements in Bootstrap3 based on device?

(11). How to visible elements based on device screen?

(12). How to show certain elements for printing purpose?

(13). What is the grid size in Bootstrap 4?

(14). How to create a bootstrap tooltip using jQuery?

(15). How to set alert using JavaScript?

(16). How to toggle a drop-down menu using JavaScript?

(17). What is the relationship between Sass and bootstrap?

(18). What is the difference between Bootstrap v3 and v4?

(19). What are cards in Bootstrap 4?

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