I am new in SCSS so bear with me :)
I have a use case where a SCSS variable --my-variable can exist and can have a value depending on some settings from the backend. So, if --my-variable exists and has a value I should override some styling. If not I shouldn't override anything.
Example:
In file1 I have:
.my-div {
color: red;
}
In file2 I should have something like this:
.my-div {
#include customize(color, --my-variable);
}
#mixin customize($property, $variable) {
#if $variable and (var($variable)) {
#{$property}: var($variable);
}
}
The problem is that the if condition inside the mixin customize() is always true even if my document has no CSS variable called --my-variable. What am I doing wrong?
Thank you
Sass has a function that check if the variable exists.
variable-exists()
$colorVariable: crimson;
#if variable-exists($colorVariable) {
// Do some styling if the variable exists
}
I'm trying to pass some CSS Custom Properties to a SASS Mixin. I'm able use the variables when applied directly in the styling I want. But when I try to use a variable in an If statement, it doesn't work.
Mixin Example:
#mixin bg-color($hue, $status) {
background: hsl($hue, 50%, 50%); // $hue works as expected
#if $status == 'danger' { // doesn't work!
color: 'red';
} #else if $status == 'warning' { // doesn't work!
color: 'orange';
} #else { // always enters the else branch
color: 'black';
}
}
CSS:
:root {
--hue: 195;
--status: 'default';
}
.demo {
#include bg-color(var(---hue), var(---status));
}
If I manually add the status value to the mixin, it works:
.demo {
#include bg-color(var(---hue), 'danger');
}
Any idea what might be the issue?
UPDATE: As #temani-afif mentioned, this approach isn't possible because SASS files are compiled before CSS variables are used.
If you have some file, where you import all SCSS files, it depends which is imported first and which are imported after.
Make sure that one that you need to be Read by VS is first.
For example i needed to read first my variables, so it have to be first, other way, my code read mixin, and doesnt know yet what is '$blue'.
I thought that I had already solved this, but the code is not compiling in the way that I intend.
Here is my current code:
$prefix: 'foo';
#mixin var-assign($var, $val) {
$var: $val !global;
};
// will output .foo-selector
.#{$prefix}-selector {
/* ... */
}
#include var-assign($prefix, 'bar');
// should output .bar-selector
.#{$prefix}-selector {
/* ... */
}
The code above prints .foo-selector twice. Where am I going wrong that I am not printing one instance of .foo-selector ad one instance of .bar-selector?
You need to changes in your mixin variable, Try using
#mixin var-assign($prefix, $val) {
$prefix: $val !global;
};
Working example here:
I want to match some strings in my class name using mixin. It works without mixins, but when I used mixin, I can't pass the variable into the string.
What was working
div[class^='myclass-'], div[class*=' myclass-'] {
#content
}
What doesn't work
#mixin startWith($name){
div[class^=$name], div[class*=' ' + $name'] {
#content;
}
}
There is a typo in your code. Use this
#mixin startWith($name){
div[class^=$name], div[class*=$name] {
#content;
}
}
TL;DR: How can you use SCSS to have CSS variables with a fallback for older browsers.
I'm trying to make sense of this article. In my opinion, you have to already be an advanced SASS user to understand it, which I'm not. To make matters worse, it's the only article I found on the subject.
Here is what I'm trying to achieve:
My scss should be along the lines of :
body {
#include v(background-color, primary)
}
then the processed CSS should be
body{
background: yellow; /* Yellow being defined above as the primary color */
background: var(--color-primary);
}
By playing around a bit, I can already get the value of the CSS variable like so:
$colors: (
primary: yellow,
);
:root {
#each $name, $color in $colors {
--color-#{$name}: $color;
}
}
#mixin background-color($color_) {
background: var(--color-#{$color_});
}
To use it:
body{
#include background-color(primary);
}
Which will result in this:
body {
background: var(--color-primary);
/* But the fallback is missing :(, I tried things with the map-get but it's really eluding me... */
}
If you're using Sass, you can automate fallbacks through a Sass mixin. Create a map of your CSS variable names and their values, and then you can look up those values in a mixin that outputs the fallback style and the preferred one
$vars: (
primary: yellow,
);
:root {
--primary: map-get($vars, primary);
}
#mixin var($property, $varName) {
#{$property}: map-get($vars, $varName);
#{$property}: var(--#{$varName});
}
The above mixin is used like so:
body {
#include var(background-color, primary);
}
and outputs the following CSS:
:root {
--primary: yellow;
}
body {
background-color: yellow;
background-color: var(--primary);
}
Et voilà :)
Update: Postcss Custom properties can do fallback and is way easier than the below code
step 1: declare scss variables
So first of all we want to put some variables in a $map, I'll go with color variables:
$colors: (
primary: #FFBB00,
secondary: #0969A2
);
step 2: automate css 4 var generation
// ripped CSS4 vars out of color map
:root {
// each item in color map
#each $key, $value in $colors {
--colors-#{$key}: $value;
}
}
What happens in root is : for each key and value in the colors map, we print the followng :
--colors-#{$key}: $value;
Which corresponds to css variable declarations. I believe the weird bit with #{} around the key is to not have spaces around the value.
Thus the result is:
--colors-primary: #FFBB00,
--colors-secondary: #0969A2
Note that the prefix (--colors-) is the same name as the scss color map above it. The why will become clear in last step.
step 3: Plenty of maps !
$props: (
background-color: $colors
);
$map-maps: (
background-color: colors
);
Here we add the map $props which maps a css property to the map containing the values. background-color will hold color, so the correct map is $colors.
map-maps is a copy of props where instead of the map we have the name of said map. (this is relative to the note in step 2).
Step 4 : let's make it work !
#mixin v($prop, $var) {
// get the map from map name
$map: map-get($props, $prop);
// fallback value, grab the variable's value from the map
$var-fall: map-get($map, $var);
// our css4 variable output
$var-output: var(--#{$map}-#{$var});
#{$prop}: $var-fall;
// css4 variable output
#{$prop}: $var-output;
}
body{
#include v(background-color, primary);
}
I simplified the code in the article quite a bit, it still works, for this example at least, the code in the article takes more into account.
Anyhow, here is what happens.
First, we call the mixin with:
#include v(background-color, primary);
Then upon entering,
$map: map-get($props, $prop); // map-get($props, background-color)
we have a variable called $map to which we assign the value that is inside the $props map at the key background-color which happen to be the $colors map. It's a bit of a maze but it's not that complicated once you resolve it.
Then for the fallback:
$var-fall: map-get($map, $var);
This simply gets the value of the map we just got (which is $colors) at the $var key (which happens to be primary). Thus the result is #FFBB00.
For the css var
$map-name: map-get($map-maps, $prop);
$var-output: var(--#{$map-name}-#{$var});
we recreate what we did to generate the var in the #each loop
Whole code would be :
$colors: (
primary: #FFBB00,
secondary: #0969A2
);
// ripped CSS4 vars out of color map
:root {
// each item in color map
#each $name, $color in $colors {
--colors-#{$name}: $color;
}
}
$props: (
background-color: $colors,
color: $colors
);
$map-maps: (
background-color: colors
);
#mixin v($prop, $var) {
// get the map from map name
$map: map-get($props, $prop);
// fallback value, grab the variable's value from the map
$var-fall: map-get($map, $var);
// our css4 variable output
$map-name: map-get($map-maps, $prop);
$var-output: var(--#{$map-name}-#{$var});
#{$prop}: $var-fall;
// css4 variable output
#{$prop}: $var-output;
}
body{
#include v(background-color, primary);
}
Now this is a simplification of what is done in the article. You should check it out to have code a bit more robust.
I assume you are aware of the reason why it didn't show the fallback. But since it's an answer I will explain the reasons
The current mixin block has only one background property which makes the sass compiler to generate only one property. I don't think sass can identify whether 'var' is supported in browser or not. So, we have to explicitly specify if we need the fallback.
Since you already have the map all you need is to get the value by giving the key 'primary'
#mixin background-color($color_) {
background: var(--color-#{$color_});
background: map-get($colors, primary);
}
This will add the background: yellow to the body class always. Alternatively if you want to control the addition of the fallback based on condition. You can do like this
#mixin background-color($color_, $showFall) {
background: var(--color-#{$color_});
#if $showFall {
background: map-get($colors, primary);
}
}
and call like this
body{
#include background-color(primary, true);
}
Code pen for the same
https://codepen.io/srajagop/pen/xdovON
Note: I am writing the answer under the assumption that you want only the background-color to work and not all the other properties like mentioned in that post. For that you need to create a proper data structure