Each component does exactly one job. The goal is to end up with many small components that are:
    easy to understand
    easy to maintain
    easy to reuse
How do you decide what is a separate component? Try to describe what it does in one sentence! When you find yourself using and and or the code you are talking about should probably be split up into two or more components.
On the other hand, when something is easily expressed in a few lines of HTML and SCSS and not likely to be reused this is a good indicator that it should not go into a separate component.

We compose with components

Usually pages use layouts as templates and will be composed of features. features are composed of components, the smallest building blocks of the app. The further down we go in this hierarchy the simpler and more generic the components become. Here is an example:
    The index page is responsible for displaying a list of posts. It uses the default layout and the PostList feature.
    The PostList feature uses a List component to render PostTeaser features.
    The PostTeaser feature consists of a LayoutCard wrapped around a CardImage, CardTitle and CardContent component.
The index page is unique in the app and will never be reused. The PostList knows it is handling post data and can therefore not be used for anything else – but it can display posts on the index as well as the user page.
The Card on the other hand does not care about the type of data it needs to handle. It just takes whatever it receives and renders it in a certain way, so it can be reused throughout the app for many different features.

We use two-word names

We follow the W3C rules for naming custom elements as suggested in the Vue.js docs to differentiate our own components from regular HTML elements in our templates.
Names should also be meaningful and unique to avoid confusion and code duplication, and also not too long to make them readable. Therefore: aim for two-word names, such as layout-card, post-list or post-teaser.

Recommended reads

For a deeper dive into the WHY and HOW have a look at the following resources which the above guidelines are based on:
Last modified 1yr ago