Day 12: max() trickery

posted on

It’s time to get me up to speed with modern CSS. There’s so much new in CSS that I know too little about. To change that I’ve started #100DaysOfMoreOrLessModernCSS. Why more or less modern CSS? Because some topics will be about cutting-edge features, while other stuff has been around for quite a while already, but I just have little to no experience with it.

I saw this interesting one-liner in a demo by Temani Afif.

.wrapper {
  margin-inline: max(0px, ((100% - 64rem) / 2)); 
}

It’s basically a shorter way of writing this:

.wrapper {
  max-width: 64rem;
  margin: 0 auto;
  width: 100%;
}

It’s not up to me to decide whether it’s smart to use this in production or not, but I want to break it down to fully understand what’s going on.

Let’s work our way from the inside out.

(100% - 64rem)

This takes the available width and subtracts the maximum width of the wrapper. What’s left is the remaining space.

((100% - 64rem) / 2)

We take the remaining space and divide it by 2. We have to divide it because we want to use it for the left and right margin of the wrapper.

max(0px, ((100% - 64rem) / 2));

If 100% is less than 64rem, we would get a negative number, which would break the layout. The max() function ensures that the margin is always at least zero. It takes a comma separated list of expressions. The largest value in the list will be selected. If the value of our calculation is less than 0, max() takes 0 instead because it’s larger than the negative number.

margin-inline: max(0px, ((100% - 64rem) / 2));

margin-inline sets both the left and the right margin to either 0 or our calculated value, which centers the element.

See on CodePen

Further reading

Overview: 100 Days Of More Or Less Modern CSS