Bootstrap Interview Questions | Freshers & Experienced

Bootstrap also known as Twitter Bootstrap is the open-source CSS framework. It aimed at responsive, mobile-first front-end web development. It holds the design templates based on CSS and JavaScript for typography, forms, buttons, navigation, and other interface components.

Reasons, why Bootstrap is used for web designing, are: -

• Easy to use: The major advantage of using bootstrap is that it occupies a ready-made block which helps the web developer to create the websites quickly. Therefore, there is no need to start from scratch. Ready-made themes are also available online.
• Massive Support Community: Bootstrap has a large support community which means you can get solutions to your issues online in a very short period. Even Bootstrap also works continuously on updating. You can imagine the community of Bootstrap on GitHub which consists of over 500 contributors and over 9000 comments.
• Come predesign with CSS, HTML and JS Elements: There are a lot of elements that we have to focus while creating the website. Heading, anchor, table, buttons, typography and images and many other topics plays a very important role in designing a website. For that, we required the knowledge of the CSS, JavaScript and HTML codes. Bootstrap makes it easy as it already possesses these elements.
• Customization as per project requirement: The Bootstrap customization page occupies JavaScript, CSS Elements, and other utilities.
• Compatible with Browser: Another benefit of Bootstrap which makes it best for the web development is that Bootstrap support all major web browser Google Chrome, Mozilla Firefox, Internet Explorer, Opera, and Safari.
• Bundle Plugin: In addition to all these benefits, Bootstrap also provides some JavaScript plugin. The users can add functionalities like sliders, dropdowns, carousels, etc., by just adding a few lines of JS code and all done on the website.

Here is a list of some major components of Bootstrap that are very important while designing the web.

Glyphicons, Dropdowns, Button groups, Button dropdowns, Input groups, Jumbotron, Page header, Thumbnails, Alerts, Progress bars, Media object, List group, Panels, Wells, Navs, Navbar, Breadcrumbs, Pagination, Labels, Badges.

Some of the major components in Bootstrap are,

• Dropdowns - They are toggle based menus that provide a list of contents.
• Button Groups - These are the set of buttons places in series adjacent to each other.
• Glyphicons - These are the formatted font icons.
• Input groups - They are used to add texts or buttons at either side of an input field.
• Alerts - It is used to provide a feedback message.
• Progress bars - It provides visual feedback on the progress of an action.
• Badges - It is used to highlight unread items.
• Pagination - It gives your site multi-page pagination.
• Jumbotron - It is used to extend the full screen to show some messages.
• Navbar - It provides navigation headers to your website.
• Button dropdowns - It creates a button element to trigger a dropdown.

The Bootstrap package includes:

• Scaffolding: Bootstrap offers a basic structure with Grid System, background and link styles.
• Components: Bootstrap consists of several reusable components built to provide dropdowns, iconography, pop-overs, navigation, alerts and much more.
• Customize: To get your version, it customizes Bootstrap's components, fewer variables, and jQuery plugins.
• CSS: Features like global CSS settings, fundamental HTML elements styled and enhanced with extensible classes, and an advanced grid system are provided in the Bootstrap.
• JavaScript Plugins: Bootstrap provides several custom jQuery plugins. Users can easily get them all, or one by one.

It allows the user to customize the presentation of their web pages to a particular extent like tablets, desktop, mobile phones and many more without changing in the markups. Media queries comprise media type, zero or many more expressions that match the condition and type of a media feature like screen resolution and device width.

There are mainly two types of layouts are available bootstrap. They are

• Fluid Layout (.container-fluid)
• Fixed Layout (.container)

In Bootstrap, a Jumbotron is a large box that is styled with large text and heavy padding for bringing extra attention to some special content or information.

Syntax: Use a <div> element with class .jumbotron to create a jumbotron:

<div class="jumbotron">
<h1>...</h1> <p>write your content</p>
</div>

The use of an offset in bootstrap is to push columns over for more spacing. Use .col-md-offset-* classes to use it on large displays.

This offset property is used to push the column over to the next cell to provide more space to the elements present in that column. To use column offset, use the .col-md-offset class.

//example
<div class="row">
  <div class="col-md-4">first column</div>
  <div class="col-md-4 offset-md-4">second column</div>
</div>

Normalize.css is used to make browsers render all elements with more consistency and in line with modern standards. It targets only those styles which need normalization.

As screens and images come in different sizes. So, to handle that, responsive images are used that automatically adjusts with the size of the screen. In Bootstrap .img-fluid class is used to make images responsive

To create a responsive image:

Add an .img-fluid class to the <img /> tag to create responsive image. The image will then fit easily to the parent element.

The .img-fluid class applies max-width: 100%; and height: auto; to the image:

Example

<img class="img-fluid" src="url.jpg" alt="Blank">

Glyphicons are widely used in web projects. These are the icon fonts to use in projects. Glyphicons Halflings are not available in free. But their creator made free for the bootstrap user. So, it is very useful if you are using Bootstrap.

A Bootstrap popover is the fascinating feature of the Bootstrap which is used to make the website look more dynamic. It is generally used to get more information about the element just by pointing the mouse pointer over that element. In the popover, if you click on any element that was previously included in your script, it will give you a message as a popover and you can see the message written in the script.

To Create Popover:

Add the data-toggle="popover" attribute to an element to create a popover. the header text and the content of the popover are defined by "title" and "data-content" attributes.

Example:

< a href="#" data-toggle="popover" title="Popover Header" data-content="Some content">Toggle popover</a>

Note: Popovers must be initialized with jQuery. Call the popover () method through the specific element.

A bootstrap card is a manageable and extensible content container in Bootstrap with some variants and options. It includes options for headers and footers, contextual background colors, powerful display options and a broad variety of content. If the user is familiar with Bootstrap 3, cards substitute our wells, old panels, and thumbnails.

Use .card class to create a basic card and write content inside the .card-body class.

Example

<div class="card">
<div class="card-body">Basic card</div> </div>

The carousel, built with CSS is a slideshow for cycling through a series of content. The content includes images, texts, or custom markups with the support of previous/next indicators.

The container is used to set the content's margins in bootstrap. It deals with the behavior of your layout. It includes the row elements which are further composed of columns. It is the most basic layout element in the bootstrap which is required when you are using the default grid system.

There are two container classes to choose from:

• .container class: It presents a responsive fixed width container.
• .container-fluid class: It provides a full-width container, spanning the entire width of the viewport.

Button group is the feature of Bootstrap 4 that allows you to group multiple buttons on a single line.

Syntax: Use .btn-grp in parent <div> element to create the button group:

Example

<div class="btn-group">
  <button type="button" class="btn btn-primary">CSE</button>
  <button type="button" class="btn btn-primary">Mech</button>
  <button type="button" class="btn btn-primary">IT</button>
</div>

The alerts in Bootstrap is used to style a predefined message to the user. The messages act as feedback to the user’s actions. Alerts are created with .alert class.

.They have contextual classes such as .alert-success, .alert-info, .alert-warning, and .alert-danger.

//example
<div class="alert alert-success">
Some success message.
</div>

<div class="alert alert-info">
Some information message.
</div>

<div class="alert alert-warning">
Some warning message.
</div>

<div class="alert alert-danger">
Some danger message.
</div>

Tooltip is a smaller popup that appears when the user places the mouse pointer over a link to an element. It then provides information about that element.

It is very useful for the new visitor to your website because they can know the purpose of links and icons with the help of this feature.

To Create Tooltip:

Add the data-toggle="tooltip" attribute to an element to create a tooltip. Use "title" attribute to display the content of tooltip.

< a href="#" data-toggle="tooltip" title="Learn Bootstrap">content </a>

Scrollspy is a Plugin. This plugin is used to automatically update the links based on the scroll position in a navigation list. It indicates which link is currently active in the viewport.

Differences between Bootstrap and Foundation

The Modal Plugin is a dialog box or a popup window that is layered over a parent window. It is displayed on top of the current page and can be meant for interaction, information or more. The purpose of the modal plugin is to display the content from other sources without leaving the current page.

Bootstrap has no dependencies. Howerever if you have to use ajax to need to add jquery file.

A source map is the factory of the information that is utilized to map the code within a compressed file back to its source. By this, you are able to designate the different source maps for each of your compressed files.

Some of the advantages of using Bootstrap are as follows: 

• The speed of your web development is vastly improved by using Bootstrap. It helps you save time by offering pre-built blocks of structured code.
• Using Bootstrap increases the responsiveness of your web application. It helps dynamically adjust your web application to a suitable screen layout.
• Bootstrap is open-source, so it can be customized to your needs. It helps you to design a website that is tailor-made according to your specifications.
• Bootstrap provides consistency in designing the application irrespective of the designer or developer.
• Bootstrap has a big community and is maintained by over 500 contributors. You get frequent updates and help from this community.

Some of the popular alternatives to Bootstrap are as follows:

• INK
• Base.
• Unsemantic.
• Materialize.
• Material - UI.
• Simple Grid-It is used to design websites with high customizability.
• HTML5 Boilerplate - It is best suited for designing adaptable websites..
• Pure.CSS - It is used to create splendid web layouts for multiple screen resolution devices.

The navigation bar or Navbar in Bootstrap is located at the top of the page that includes the support for branding, navigation, and collapse plugin. The default navigation bar is created with the class <nav class=”navbar navbar-default”>.

The sub-components of the navigation bar are .navbar-brand, .navbar-nav, .navbar-toggler, .form-inline, .navbar-text, and .collapse.navbar-collapse. Each component has its own functions.

Badges in Bootstrap is used to highlight new or unread items in your web application. It is similar to the labels but has more rounded corners. You can use the class "badge" to create a badge.

//example
<a href = "#">Messages <span class = "badge"></span></a>

The progress bar in Bootstrap is used to provide visual feedback to the user on the progress of the action or process on the website. The default progress bar can be used by the .progress class in an element.

You can also create a progress bar with labels, colors, striped colors, animation, and stacked bars.

//example
<div class="progress">
  <div class="progress-bar" role="progressbar" aria-valuenow="70"
  aria-valuemin="0" aria-valuemax="100" style="width:70%">
    <span class="sr-only">70% Complete</span>
  </div>
</div>

Labels in Bootstrap is used to provide additional information like tips, offering counts to the user. The default label can be used with .label class. The appearance of the label can be modified by using the sub-components such as label-primary, label-success, label-info, label-warning, and label-danger.

//example
<h1>Example of the default label class <span class = "label label-default">Label</span></h1>

The supported form controls in the bootstrap are input, text area, button, checkbox, radio, and select.

Thus, these interview questions cover mostly all the important elements and functions of bootstrap, which an interviewer can ask you. Prepare these sets of questions so that you can stand out of the competition.