Summary - Component library

Build a component library skeleton with BEM and cascade layers.

Component library skeleton

A component library gathers reusable interface parts in one place: buttons, cards, forms, alerts. Each component is named with BEM and its styles live in @layer layers. The library then stays consistent and easy to change across apps.

A typical skeleton: a base layer for reset and typography; a components layer with a section per component; a utilities layer for helper classes. Changing one component touches only that section; no clash, low specificity, easy maintenance.

Exercise Add a button to the component library

Add the @layer base, components; order at the top. Then inside an @layer components block, write a BEM trio: .button block with display: inline-flex; .button--primary modifier with background: navy and color: white.

Show example solution

/* add the layer order and the button BEM */
@layer base, components;

@layer components {
  .button {
    display: inline-flex;
  }
  .button--primary {
    background: navy;
    color: white;
  }
}

How the skeleton grows

A component library grows over time. Adding a new component means: open a new BEM block in the components layer and use those classes in HTML. The risk of breaking old components stays low because every class is flat and tied to a layer.

The summary of this approach: names with BEM (block, element, modifier), order with @layer, specificity low with flat classes. Together they keep CSS consistent and easy to maintain even in large projects.

Test yourself

Match each architecture piece to its role

base layer

Reset and typography
components layer

Component styles
utilities layer

Helper classes
.button--primary

BEM modifier
Which approach is recommended for a component library?
- BEM names + @layer layers
- A single style.css + !important
- Id selectors + nested selectors
- Type selectors only
Show answer

BEM names + @layer layers — Correct. BEM classes are flat and low-specificity; @layer controls clashes through layer order.

Next lesson: What is CSS performance?

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