cssLess – Variables

Variables are nicknames or shorthand used to refer to other elements in your code. In Less, it’s common to use variables in place of color names and font stacks.

Step 1: Creating variables

A variable has two parts: the unique name you create for it and the value it stands in for. The name and the value are separated by a colon (:). You can name your variables any way that makes sense for you, so long as they follow these basic rules; all variable names:

• must begin with an ‘at’ symbol (@)
• cannot begin with a number:
  • ✅ @test1 is valid
  • ❌ @1test is not
• cannot have spaces in their name:
  • ✅ @test-one is valid
  • ❌ @test one is not

Ideally, you should declare your variables at the top of your stylesheet so they can be easily reused throughout the rest of your Less code.

Example

The monospace font used on this site is called Source Code Pro ✳️ . In CSS, whenever I want to use this font, I have to reference the entire font stack, like so:

code {
  font-family: "Source Code Pro", "Andale Mono", AndaleMono, Courier, monospace;
}

On this page alone, there more than five elements using this font. That repetition is a chore and usually involves copying and pasting the entire font-family declaration from another spot in my stylesheet. But there’s an easier way! 🌈

Instead, using Less, I can define a variable to represent the entire font stack and reuse it any time I want to use this specific monospace font.

@font-mono: "Source Code Pro", "Andale Mono", AndaleMono, Courier, monospace;

Step 2: Using variables

⚠️ Remember that you cannot use a variable in your stylesheet without first creating it and assigning its value. Attempting to do so will cause an error when Less attempts to convert your code into CSS.

After I have named my variable (@font-mono) and assigned its value (the monospace font stack I’m using), I can now use it on any element where I want to use my monospace font:

code {
  font-family: @font-mono;
}

And when the Less compiles to CSS, it will look exactly like the first code example on this page. 🎉

Why use variables

Because you control the naming of your variables, they provide an easy way to replace hard-to-remember bits of CSS with something you’ve chosen the name for instead. @font-mono is significantly easier for me to remember than the entirety of my monospace font stack.

This is why variable names are great for replacing colors, too. On this site, I use specific shades of green and yellow as accent colors. Because I use Less variables, I don’t have to remember the exact color values or even remember which is which. Is #A2F1C1 green or yellow? 🤷🏻‍♀️ I don’t know and I don’t have to care because I use variables instead. When I want green, I say exactly that:

div {
  background-color: @color-mint;
}

Variables are also a useful tool to maintain consistency. For example, on this site, instead of creating unique values everywhere for my margins and paddings, I mostly limit myself to five values, and I’ve named a T-shirt sized variable for each:

// SPACING
@spacing-xs: 8px;
@spacing-sm: 12px;
@spacing-md: 16px;
@spacing-lg: 40px;
@spacing-xl: 64px;

It’s more typing to add @spacing-xl than the actual value, but using variables helps keep my spacing consistent, even as I adapt the site styles from mobile to desktop.

When to use variables

There is definitely a sweet spot with variables – too many and they be hard to remember or differentiate. Questions to ask yourself before creating a variable:

• Is this value used in more than one place? If not, hold off. For example, if I used my monospace font stack on the body element and then never changed the font, I wouldn’t create a variable for that.
• Am I likely to want to change or tweak this value? If so, creating a variable makes sense because it means I only have to make the change in one place, not all over my stylesheets.
• Is the value meaningful? This one is harder to explain simply, but it prevents creating variables just because you can. For example, I can create a variable for the value of 3 pixels, like so:

@pixels-3: 3px;

And then I can use that in all sorts of places in my styles:

h1 {
  margin-top: @pixels-3;
}
main {
  border: @pixels-3 solid green;
  padding: @pixels-3;
}

This is totally valid Less, but it’s not really helpful. The margin on my h1 and the border on my main element don’t really have anything in common; if I want to change the margin on the h1, that’s unlikely to affect my thinking about my border styles.

Try it

1. Remix this project on Glitch
   • This uses the same markup and styles from the lesson on organizing your CSS
2. Open and look at the styles.less file.
   • Other than updating the format of some of the comments, this file is unchanged from the earlier lesson. I just copied and pasted the whole original CSS file.
   • This is the file you should be editing.
3. In the styles.less file, change the color palette (lines 5-9) into Less variables.
4. Use the variables in place of the HSL values in the remainder of the stylesheet.

If you attempt to use a variable that you haven’t created, Glitch will show an error at the top of the page, like so:

NameError: variable @nonesuch is undefined
in styles.less on line 48, column 21:

47 body {
48   background-color: @nonesuch;
49   color: hsl(190, 5%, 15%);

This error tells me:

• I’m attempting to use a variable before I’ve created it (variable … is undefined)
• What the invalid variable name is (@nonesuch)
• What file it’s in (styles.less)
• What line it’s on (line 48)

Which should be all the info you need to fix the issue. Thanks, Glitch! 😄

For the purposes of this demo, you should not need to make changes to the HTML document.

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