What exactly Bootstrap is?

• style guide + code snippets = DESIGN SYSTEM 💖

Put simply:

• css + js snippets
• guide for developers with no taste

5 reasons to fall in love with Bootstrap 4

1) Goodbye {less}, Hello Sass 👋

Big step for Sass

• Less is in Js (@ - syntax)
• Sass was in Ruby (this year they switch to Js as well) ($ - syntax, scss)

LESS

@primary-color: seashell;
@primary-bg: darkslategrey;

body {
  color: @primary-color;
  background: @primary-bg;
}

SCSS

$primary-color: seashell;
$primary-bg: darkslategrey;

body {
  color: $primary-color;

  background: $primary-bg;

}

Compiled CSS

body {
  color:seashell;
  background: darkslategrey;
}

2) Flexbox is on fire 🔥

• Bootstrap 3.x - float-based style (always problems with clearfix)
• Bootstrap 4.x - flexbox grid by default^

^fully supported by IE10+ & Edge

Means:

• auto-layout columns ANY number of columns
• combined with 12-col grid known from previous version
• more control of both height and width

Auto-layout example:

12-col grid:

Bootstrap 3:

<div class="row">
   <div class="col-xs-2">.col-xs-2</div>
   <div class="col-xs-4">.col-xs-4</div>
   <div class="col-xs-6">.col-xs-6</div>
</div>

Bootstrap 4:

<div class="row">
   <div class="col-2">.col-2</div>
   <div class="col-4">.col-4</div>
   <div class="col-6">.col-6</div>
</div>

Horizontal alignment

Goodbye offset, hello justify-content!

Bootstrap 3

<div class="row">
    <div class="col-xs-6 col-xs-offset-3">This column is now centered.</div>
</div>

Bootstrap 4

<div class="row justify-content-center">
    <div class="col-6">All columns in that row will be automatically centered.</div>
</div>

But: If you didn’t know how to use flexbox, it's high time to learn!

e.g. with flexbox cards here: https://codepen.io/ritawanderlust/pen/KejyOE

3) REM sizing ✍️

• REMs are a way of setting font-sizes based on the font-size of the root HTML element.
• They also allow you to quickly scale an entire project by changing the root font-size (for example at a certain media query/screen size)

pls, forget about: just use pixels - easy to make accessibility faux pas

4) RWD reakpoint improvements 👁

Bootstrap 3

Bootstrap 4

We now have xs, sm, md, lg, and xl.

• Extra small (xs) - below 576px
• Small (sm) - between 576px and 768px
• Medium (md) - between 768px and 992px
• Large (lg) - between 992px and 1200px
• Extra Large (xl) - over 1200px (4k ready)

This also means every tier has been bumped up one level

(so .col-md-6 in v3 is now .col-lg-6 in v4).

5) Pleasuring developers - little useful things 🎁

Documentation Utilities (borders, paddings, responsive floats, clearfix...) Variables customizing like:

• Colors
• Options (Flex Box, transitions, rounded, shadows, etc.)
• Spacing
• Body (defaults)
• Link Styles
• Grid Breakpoints
• Grid Containers
• Grid Columns
• Typography
• Components
• Tables

Overwritting Bootstrap caused many mistakes and bad practices.

Bootstrap 4 proposes us "sassy" style guide / modular changes instead overwritting ;)

Nice to mention:

• file reboot added
• removed custom builder - modular sass structure ( _utilities.scss, _variables.css, _reboot.scss etc..)
• removed glyphicons (you decide what to use: Glyphicons/FontAwesome/Iconic/Octicons)
• cards instead of pannels