Learning CSS Grid - Basics

Finally I need a CSS grid. Here is my intro to it. If you prefer a video this one (28 minutes) explains grid basics very well. But before learning CSS grid, I need to answer the question if I need it. I know flexbox quite ok, so why not use flexbox.

The Question: Flexbox or Grid?

MDN states flexbox best suits for one dimensional (row or column) and grid for two-dimensional layouts.

The most helpful explanation is given on the MDN page, distinguishing the two use cases quite well:

An ideal use case for flexbox is when you have a set of items and want to space them out evenly in a container. You let the size of the content decide how much individual space each item takes up.

When you use CSS Grid Layout you create a layout and then you place items into it, or you allow the auto-placement rules to place the items into the grid cells according to that strict grid.

The shorter, but less explicit one is:

A simple question to ask yourself when deciding between grid or flexbox is:

• do I only need to control the layout by row or column – use a flexbox
• do I need to control the layout by row and column – use a grid

I like to start using it as simple as possible, doing baby steps. I start with display: grid and grid: ... properties.

CSS Property grid

The CSS property grid (MDN site) is a shorthand perfect for a simple grid setup to learn the power of CSS grid.

I use a surrounding HTML tag <section> that wraps our grid, it gets the display:grid property and the grid's layout is determined by the grid property:

<section class="grid">
  <span>&updownarrow; ...</span>
  ...
</section>

<style>
  .grid {
    display: grid;
    grid: 3rem 100px / 1fr 50px 2fr;
  }
</style>

It renders like this:

The / in the grid: ... property separates the definition for the row heights and column widths

grid: <row heights> / <column widths>

The use of the grid shorthand only reflects part of what it can do. Some explanations about the above code, if its all obvious skip them:

• The display: grid must be set, on the container that will be the grid, here the <section>.
• The grid: ... property defines a grid template, consisting of the columns widths and the rows heights.
• Only every row and column that is defined in the template is rendered with the given dimensions.
• All row heights after the 2nd row fall back to auto.
• We defined eleven SPANs, the grid template only defined three columns, a new row starts every three columns.
• The unit fr is described in the spec like this:

  A flexible length or <flex> is a dimension with the fr unit, which represents a fraction of the leftover space in the grid container.

The short intro to the grid property makes it already possible to use it and create various grids.

CSS Property grid-template

Above we used the shortest shorthand version, the CSS property grid.

grid: 3rem 100px / 1fr 150px 2fr;

The following means and renders the same. It is just a bit more explicit, still a shorthand for defining the row and column dimensions.

grid-template: 3rem 100px / 1fr 150px 2fr;

The explicit version is the following, and still renders exactly like all above.

grid-template-rows: 3rem 100px;
grid-template-columns: 1fr 150px 2fr;

Let's see how to be a bit more flexible, using a CSS function repeat.

CSS Function repeat()

Above I defined very explicit how many columns, how many rows and their dimensions. Using the CSS function repeat() allows recurring pattern, like here:

display: grid;
grid: repeat(2, 3rem 100px) / repeat(3, 1fr); 

The function repeat(2, 3rem 100px) repeats 3rem 100px twice.
And repeat(3, 1fr) for the rows it repeats 1fr three times.