Related
On my website, I'm constantly doing style="font-size: #ofpx;". However, I was wondering if there's a way to do it with scss so that, when I declare a class, it would also change the font size. For example:
<div class='col-lg-4 font-20'>whatever here</div>
and this would change my font-size to 20. If I did font-30, it would change my font-size to 30 and etc...
What I have so far:
.font-#{$fontsize} {
font-size: $fontsize;
}
This can't be done for arbitrary sizes. The nature of SCSS is that is needs to be flattened down to CSS before it gets applied to the HTML. What you are asking for, however, is essentially to create rules at run-time rather than compile-time.
In other words, SCSS makes it easier to write some of the repetitive parts of CSS, but it doesn't allow you to do anything new that wasn't already possible with plain old CSS.
What you're asking for is also a code smell. It smells like your markup isn't semantic enough. The purpose of a CSS class is to group objects with similar characteristics, but you're using them instead to describe the styles they impart. I would suggest stepping back and reconsidering what it is that you really want.
You obviously have details of certain elements that are context-dependent. For example, maybe you are applying these rules to buttons when you want to make them smaller or larger than usual. You need to identify the scenarios in which the buttons change. Maybe they are 20% smaller if they are in a modal dialog? Then write your normal .button rules, and also create rules for .modal .button which make it smaller.
If you're positive that you want to define font-size for each element within the HTML (and sometimes there are good reasons for doing so), just continue using inline styles. The only reason inline styling is frowned upon is because it combines model and view logic in a way that harms reusability; however, what you are requesting does so in exactly the same way. This is what inline styles were made for. Don't re-invent the wheel.
With all of that said, you can use sass loops to automatically generate classes for integers within a range. For example:
/* warning: this is generally a bad idea */
#for $i from 1 through 100 {
.font-#{$i} {
font-size: #{$i}px;
}
}
This is not a good idea. Pragmatically speaking it doesn't offer any advantages over just using inline styles and with large ranges your resulting file will be larger (which affects website load times).
Aside: There is a CSS philosophy (or fad, if you're feeling ungenerous) called Atomic CSS (or sometimes Functional CSS) which defies the classical advice given in this answer. I won't give an opinion on its effectiveness at producing clean, maintainable code, but it does typically require more tooling than SCSS alone if used with the degree of specificity requested in this question.
Just going to add, mixins are great, but if you want a util class (attach a class to an element, get that font-size applied to it, do a for-loop in SCSS like so..
#for $i from 1 through 4 {
$fontsize: 10px * $i;
.font-#{$i} {
font-size: $fontsize;
}
}
compiles to
.font-1 {
font-size: 10px;
}
.font-2 {
font-size: 20px;
}
.font-3 {
font-size: 30px;
}
.font-4 {
font-size: 40px;
}
If you want the class to match the # of pixels...
#for $i from 1 through 4 {
$base: 10;
$fontsize: $base * $i;
.font-#{$fontsize} {
font-size: $fontsize + 0px;
}
}
Which compiles to
.font-10 {
font-size: 10px;
}
.font-20 {
font-size: 20px;
}
.font-30 {
font-size: 30px;
}
.font-40 {
font-size: 40px;
}
Codepen example.
When using "words" instead of "numbers" for variables, and the word not being at the end of the classname. I could work something out using CSS Attribute selectors ("wildcard selector"). I can iterate over a map object, and use text values to build CSS selectors.
SASS
//map
$colors: (
primary: #121212,
success: #8bcea8
);
//loop
#each $color, $value in $colors {
//can't do this: div.first-class.is-style-#{$color}-component
//can do this:
div.first-class[class*="is-style-#{$color}-component"] {
background-color: $value;
}
}
HTML
<div class="first-class is-style-primary-component"></div>
This will generate a div.myComponent[class*="is-style-primary-component"] selector and so <div class="first-class is-style-primary-component"></div> (.first-class is not required, selector could be div[class*="is-style-#{$color}-component"] or even [class*="is-style-#{$color}-component"] only).
Yet, in some cases of CSS class naming, it could be limited due to the wildcard selector, which is "larger" than a specific class selector rule.
Of course, inline style tags are bad form. So yes, you should add some classes for font size, or just set font size on the elements you need to as you go. Up to you. If you want, you could use a mixin like so:
#mixin font-size($size) {
font-size: $size;
}
.some-div { #include font-size(10px); }
But that's probably overkill unless you get a group of rules that usually go together.
Just for those of you who might stumble across this question in a more recent time and are new to FrontEnd Development.
What Woodrow Barlow said about using inline-styles instead of rule specific classes isn't quite an up-to-date opinion. For instance, Bootstrap has some of those and Tachyons is entirely built upon them. Actually this practice is called Atomic CSS or Functional CSS.
It's better explained by John Polacek in his CSS Tricks article:
https://css-tricks.com/lets-define-exactly-atomic-css/
You can use mixins like this
#mixin font($fontsize) {
font-size: $fontsize;
}
.box {
#include font(10px);
}
One feature I really love with LESS is nested rules. It makes the stylesheet much cleaner that way and you can find an element very quickly.
I was wondering if there's an option when compiling to optimize selectors. For example...
#global {
/* Styles here maybe */
.container {
/* Styles here maybe */
#sidebar {
/* Styles here maybe */
.title {
font-weight: bold;
}
}
}
}
will be compiled to #global .container #sidebar .title { font-weight: bold; }.
But the first two selectors are useless, since #sidebar should be unique in my page.
Is there a way to ask LESS to compile this to #sidebar .title { font-weight: bold; } instead?
Your assumption is wrong that multiple IDs in CSS are redundant. Imagine, as an example, a site where the CMS generates the page type into the output, like that it's the contact page:
<body id="contact">
<section id="content">Blah</section>
</body>
According to your logic, the following piece of CSS would be a candidate for 'optimization':
#contact #content {
background:red;
}
Now however, your home page has <body id="home"> of course in this imaginary CMS. And suddenly the content of your homepage has a red background because you decided to erroneously optimize that #contact selector out of the CSS, while it most certainly shouldn't have a red background according to this rule.
So no, LESS cannot do this because it would break code. If you don't want the selectors, don't use them and don't put them in your code.
Other answers, including the accepted one, have explained convincingly why LESS cannot simplify your nested selectors in the way you want.
Actually, SASS has the ability to do this:
#global {
.container {
#at-root #sidebar {
.title {
font-weight: bold;
The #at-root directive essentially ignores all the higher nesting selectors. I don't know if LESS has something similar. The above compiles into simply
#sidebar {
.title {
font-weight: bold;
But there is a deeper issue here, starting with the fact that you "love" nested rules in LESS. Stop loving them quite so much. I don't know about you, but most people love nested rules because they think it's cool to exactly mimic the hierarchical structure of their HTML. The SASS docs even claim this as a benefit:
Sass will let you nest your CSS selectors in a way that follows the same visual hierarchy of your HTML.
So people with HTML such as
<div class="foo">
<ul>
<li class="item">
write LESS like
.foo {
ul {
li.item {
This is a horrible, horrible idea, It makes the structure of CSS completely dependent on the structure of the HTML. If you change one nesting level in the HTML, your CSS breaks. Often this approach is combined with a lot of rules defined against tag names such as ul instead of class names, which aggravates the dependency, so changing the ul to ol in the HTML breaks the rules again. Or it's combined with rules based on Bootstrap classes such as col-md-6, so if you ever change that to col-md-4 things break again.
CSS rules should be orthogonal to the HTML. They represent a different dimension. They represent styling concepts which are applied selectively throughout and across the HTML.
I am guessing that you wrote
#global {
.container {
#sidebar {
.title {
font-weight: bold;
because you are adopting this mistaken idea of mirroring the HTML structure in your LESS. Then, you notice that this compiles down to having selectors which contain multiple IDs, which you imagine must be inefficient (although, actually, the degree of inefficiency is minimal). You yourself are writing extraneous nesting levels in your LESS, then complaining that they may be slowing down performance!
Worse, you've hard-wired assumptions about the HTML structure into your CSS. It's of no consequence that the sidebar happens to fall inside a .container which is inside a global element. So don't write them. Perhaps at some point you decide to change the container class to container-fluid. Boom, instantly your CSS breaks. What is the point of conditionalizing the fact that the title should be bold on it being contained with a container class, which in any case is a layout-related class that has (or should have) nothing to do with styling? If you're going to duplicate your HTML structure in your CSS using preprocessor nesting, just go back to writing inline styles. At least that way you'll only have one file to change when you change your HTML around.
When designing CSS, you should think just as hard about the design of the rules as you do about the design of classes and methods when writing JS. In this case, you need to ask yourself, "What characterizes the situation where I want some title to be bold? What drives that? What is the nature of boldness? What am I indicating by boldness? What is the semantic notion indicated by boldness?"
Let's say that you want all titles to be bold. Then you simply say that:
.title { font-weight: bold }
Let's say that you want a title to be bold only when it's in the sidebar. Then you simply say that:
#sidebar .title { font-weight: bold; }
My suggestion here is to go cold turkey. Stop using nesting during a withdrawal period. Write rules with the minimum number of selector components. Refactor your classes to have semantic names (such as title-emphasis). Once you're "sober", you can go back to cautiously using LESS's nesting capability when it is useful, such as perhaps for hover:
#boo {
color: red;
&:hover {
color: blue;
}
}
This is actually useful and saves you from writing #boo twice, and groups the rules in an easy-to-understand way.
I have a vague memory, but can't find anything on it, about being able to use a keyword "with" or "like" to do something similar to the following.
using .class1{
#a1, #a4{color:#ffffff;}
#a2{color:#dddddd;}
#a3{color:#eeeeee;}
}
instead of having to write:
.class1 #a1, .class #a4{color:#ffffff;}
.class2 #a2{color:#dddddd;}
.class3 #a3{color:#eeeeee;}
The issue is that I'm including some html/css in a page and the css is screwing up the rest of the page. So, I'd like to modify the css so it only affect the small portion, rather than the whole page. I'm doing all this programmatically on a large number of pages, so it'd be much easier to just wrap all of the new css in something like "using .class1" rather than parsing through the css and add .class1 to the beginning of every selector.
Any ideas? thanks!!
There is no way to achieve what you want unless you use some CSS preprocessor like SASS. Here's how it would look when done using SASS:
.class1 {
#a1, #a4 {
color: #ffffff;
}
#a2 {
color: #dddddd;
}
#a3 {
color: #eeeeee;
}
}
Reference: little link.
Wrap the block of included HTML in its own ID like #overRideCSS
Then if you ever need to over-ride specific styles, you can preface your selector with that ID:
#overRideCSS <other selectors> {etc...}
I'm not sure what to call this, but basically let's say I have a style that I use a lot,
.somepattern{
font-size:16px;
font-weight:bold;
border:2px solid red;
}
but sometime I want to change the font-size and the color for border. Is it possible to treat this code as a library, where I can set the style to a div
<div class="somepattern">Text</div>
but still control the 16px and red like we do with functions?
I know I'm late to the party but the selected answer IS NOT the right answer since it's deferring it to CSS preprocessors.
To answer the specific question "Do CSS functions exist?", the answer is: Yes.
However, CSS functions work completely different than the OP's concept initially is.
cuixiping's answer seems the most correct answer.
Examples of CSS functions are:
url()
attr()
calc()
rotate()
scale()
linear-gradient()
sepia()
grayscale()
translate()
A detailed, comprehensive list can be found here:
CSS functions on MDN Updated link 18/9/20
You can't programatically control CSS from your markup, but you can use one of the many CSS extensions to make CSS work more like a compiled language.
http://lesscss.org/
http://sass-lang.com/
If we wrote your example in LESS, we'd get something like this:
.somepattern(#color: red, #size: 16px) {
font-size:#size;
font-weight:bold;
border:2px solid #color;
}
And then you could use it in your LESS file like so:
.myclass {
.somepattern(green, 20px);
}
Nope. No CSS functionality like you require. At least not directly.
But there are at least two rather generic ways for you to use to accomplish what you need:
Class combining
You can of course combine as many classes as you like in any element like:
<div class="heading run-in">
Some heading
</div>
Lorem ipsum dolor sit amet...
and you'd have CSS defined as:
.heading {
color: #999;
font-size: 16pt;
font-weight: bold;
border-bottom: 2px solid red;
display: block;
margin: 1.5em 0 .5em;
}
.run-in {
display: inline;
margin: 0;
font-size: 1em;
}
LESS CSS
And there is of course LESS CSS project that lets you define variables (and has other sugars as well) and use them in other classes.
LESS extends CSS with dynamic behavior such as variables, mixins, operations and functions. LESS runs on both the client-side (IE 6+, Webkit, Firefox) and server-side, with Node.js.
If your server platform is .net there's a project DotLessCSS with a library in .net as well. And there's also T4 template by Phil Haack.
Mind that there are many CSS preprocessors/enhancers like LESS CSS as well:
SASS
xCSS
HSS
CleverCSS
And probably some others that I didn't mention. Some support nesting CSS3 selectors as well others don't. Some are aimed at particular server-side technology some don't. So choose wisely.
you can redefine style by adding the style tag to your HTML:
<div class="somepattern" style="font-size:5px">Text</div>
or by applying multiple classes like class="somepattern small".
HTML
<div class="somepattern small"> Text </div>
CSS
.small {
font-size:5px;
}
the small class will be applied after the somepattern class and will therefore override any properties set in the some pattern class.
Even later to the party!
You can now do this with css custom variables.
In our css using the var() function:
.some-pattern {
font-size: var(--font-size);
font-weight: bold;
border: var(--border);
}
Then in our html defining the custom variables inline:
<div
class="some-pattern"
style="--border: 3px double red; --font-size: 16px;"
>
test
</div>
What you described is actually done with style attribute.
<div class="somepattern" style="font-size:10px;">Text</div>
I think this is exactly what you want. And it is not recommended, because it breaks the usual (good) pattern of spitting content and its visual style. (Although, honestly, I do use it a lot. ;-))
its a css class. It cannot be used like functions if that's what you are asking. There is no code library as its not a compiled. CSS is just presentation semantics (formatting) of a document written in a markup language. You can include all css classes in a .css file and use it where ever you want instead.
I've come to realize through the comments of others that this solution overcomplicates the problem at hand. This solution works but there are easier and better alternatives that do not depend on server-side scripting.
You can actually control your stylesheet if you make it a php file stylesheet.php?fontsize=16 and then inside your stylesheet you can retrieve the variable
<?php
header("Content-type: text/css");
$fontsize=16;
?>
.somepattern{
font-size: $fontsize;
font-weight:bold;
border:2px solid red;
}
Yes, it's possible. But you have to make it on your own with the help of Recatjs(u don't have to go deeper, basic is enough for this). Actually, think like that If bootstrap can make such things where we just have to define the class name and it automatically designes HTML files, then why we cannot do it.
Here's the image of my code(https://i.stack.imgur.com/hyePO.png)
and this is how I used it in my jsx code (https://i.stack.imgur.com/yK6VD.jpg)
Do you mean inline styles ? <div class="somepattern" style="border-color:green">Text</div>
Is there any way to use conditional statements in CSS?
I'd say the closest thing to "IF" in CSS are media queries, such as those you can use for responsive design. With media queries, you're saying things like, "If the screen is between 440px and 660px wide, do this". Read more about media queries here: http://www.w3schools.com/cssref/css3_pr_mediaquery.asp, and here's an example of how they look:
#media screen and (max-width: 300px) {
body {
background-color: lightblue;
}
}
That's pretty much the extent of "IF" within CSS, except to move over to SASS/SCSS (as mentioned above).
I think your best bet is to change your classes / IDs within the scripting language, and then treat each of the class/ID options in your CSS. For instance, in PHP, it might be something like:
<?php
if( A > B ){
echo '<div class="option-a">';
}
else{
echo '<div class="option-b">';
}
?>
Then your CSS can be like
.option-a {
background-color:red;
}
.option-b {
background-color:blue;
}
No. But can you give an example what you have in mind? What condition do you want to check?
Maybe Sass or Compass are interesting for you.
Quote from Sass:
Sass makes CSS fun again. Sass is CSS, plus nested rules, variables, mixins, and more, all in a concise, readable syntax.
CSS itself doesn't have conditional statements, but here's a hack involving custom properties (a.k.a. "css variables").
In this trivial example, you want to apply a padding based on a certain condition—like an "if" statement.
:root { --is-big: 0; }
.is-big { --is-big: 1; }
.block {
padding: calc(
4rem * var(--is-big) +
1rem * (1 - var(--is-big))
);
}
So any .block that's an .is-big or that's a descendant of one will have a padding of 4rem, while all other blocks will only have 1rem. Now I call this a "trivial" example because it can be done without the hack.
.block {
padding: 1rem;
}
.is-big .block,
.block.is-big {
padding: 4rem;
}
But I will leave its applications to your imagination.
The #supports rule (92% browser support July 2017) rule can be used for conditional logic on css properties:
#supports (display: -webkit-box) {
.for_older_webkit_browser { display: -webkit-box }
}
#supports not (display: -webkit-box) {
.newer_browsers { display: flex }
}
The only conditions available in CSS are selectors and #media. Some browsers support some of the CSS 3 selectors and media queries.
You can modify an element with JavaScript to change if it matches a selector or not (e.g. by adding a new class).
I would argue that you can use if statements in CSS. Although they aren't worded as such. In the example below, I've said that if the check-box is checked I want the background changed to white. If you want to see a working example check out www.armstrongdes.com. I built this for a client. Re size your window so that the mobile navigation takes over and click the nav button. All CSS. I think it's safe to say this concept could be used for many things.
#sidebartoggler:checked + .page-wrap .hamb {
background: #fff;
}
// example set as if statement sudo code.
if (sidebaretoggler is checked == true) {
set the background color of .hamb to white;
}
CSS has become a very powerful tool over the years and it has hacks for a lot of things javaScript can do
There is a hack in CSS for using conditional statements/logic.
It involves using the symbol '~'
Let me further illustrate with an example.
Let's say you want a background to slide into the page when a button is clicked. All you need to do is use a radio checkbox.
Style the label for the radio underneath the button so that when the button is pressed the checkbox is also pressed.
Then you use the code below
.checkbox:checked ~ .background{
opacity:1
width: 100%
}
This code simply states IF the checkbox is CHECKED then open up the background ELSE leave it as it is.
css files do not support conditional statements.
If you want something to look one of two ways, depending on some condition, give it a suitable class using your server side scripting language or javascript. eg
<div class="oh-yes"></div>
<div class="hell-no"></div>
There is no native IF/ELSE for CSS available. CSS preprocessors like SASS (and Compass) can help, but if you’re looking for more feature-specific if/else conditions you should give Modernizr a try. It does feature-detection and then adds classes to the HTML element to indicate which CSS3 & HTML5 features the browser supports and doesn’t support. You can then write very if/else-like CSS right in your CSS without any preprocessing, like this:
.geolocation #someElem {
/* only apply this if the browser supports Geolocation */
}
.no-geolocation #someElem {
/* only apply this if the browser DOES NOT support Geolocation */
}
Keep in mind that you should always progressively enhance, so rather than the above example (which illustrates the point better), you should write something more like this:
#someElem {
/* default styles, suitable for both Geolocation support and lack thereof */
}
.geolocation #someElem {
/* only properties as needed to overwrite the default styling */
}
Note that Modernizr does rely on JavaScript, so if JS is disabled you wouldn’t get anything. Hence the progressive enhancement approach of #someElem first, as a no-js foundation.
Changing your css file to a scss file would allow you to do the trick. An example in Angular would be to use an ngClass and your scss would look like:
.sidebar {
height: 100%;
width: 60px;
&.is-open {
width: 150px
}
}
While this feels like a bit of a hack, and may not work perfectly in all browsers, a method I have used recently combines the fact that CSS (at least in Chrome) seems to ignore invalid values set on properties, and we can set custom properties that fall back to their default value when invalid.
(Note: I haven't deeply tested this, so treat it as a hacky proof of concept/possible idea)
The following is written in SCSS, but it should work just as well in standard CSS:
.hero-image {
// CSS ignores invalid property values
// When this var is set to an image URL, the browser will ignore it
// When this var isn't set, then we will use the default fallback for the var, which is 'none'
display: var(--loading-page-background-image, none);
// This part isn't directly relevant to my 'if' example, but shows how I was actually using this custom property normally
background-image: var(--loading-page-background-image, none);
}
I'm setting the custom property from JavaScript / React, but it would likely work regardless of how you set it:
// 'true' case
const chosenLoaderUrl = "https://www.example.com/loader.png";
// 'false' case
//const chosenLoaderUrl = "";
// containerRef is just a reference to the div object, you could get this with
// jquery or however you need. Since I'm in React, I used useRef() and attached
// that to my div
containerRef.current.style.setProperty(
"--loading-page-background-image",
`url(${chosenLoaderUrl})`
);
When chosenLoaderUrl is set to my url, that url is an invalid value for the display property, so it seems to get ignored.
When chosenLoaderUrl is set to an empty value, it falls back to the default value in my var() statement, so sets display to none
I'm not sure how 'generalisable' this concept it, but figured I would add it to the other suggestions here in case it is useful to anyone.
Your stylesheet should be thought of as a static table of available variables that your html document can call on based on what you need to display. The logic should be in your javascript and html, use javascript to dynamically apply attributes based on conditions if you really need to. Stylesheets are not the place for logic.
You can use combination of jquery and css classes i.e. I want to change a font color of certain element depending on the color of the background:
CSS:
.h3DarkMode{
color: lightgray;
}
.h3LightMode{
color: gray;
}
HTML:
<h3 class="myText">My Text Here...</h3>
JQuery:
var toggleMode = localStorage.getItem("toggleMode");
if (toggleMode == "dark"){
$(".myText").removeClass("h3LightMode").addClass("h3DarkMode");
}else{
$(".myText").removeClass("h3DarkMode").addClass("h3LightMode");
}
No you can't do if in CSS, but you can choose which style sheet you will use
Here is an example :
<!--[if IE 6]>
Special instructions for IE 6 here
<![endif]-->
will use only for IE 6 here is the website where it is from http://www.quirksmode.org/css/condcom.html , only IE has conditional comments. Other browser do not, although there are some properties you can use for Firefox starting with -moz or for safari starting with -webkit. You can use javascript to detect which browser you're using and use javascript if for whatever actions you want to perform but that is a bad idea, since it can be disabled.