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SCSS extend a nested selector and override the nested rulesets
(4 answers)
Closed 7 years ago.
I'm pretty new to SASS and I'm currently using a library written in SASS.
I would like to override not only variables from this library but also styles for a few bits. How can I override this style without duplicating CSS for that specific class ?
To be clear, let's say I have this class in my library which I import in my main.scss:
.twitter-foo {
float: none;
}
Now in my own file:
.twitter-foo {
float: a lot more;
}
Then my output is:
.twitter-foo {
float: none; // overriden!
}
.twitter-foo {
float: a lot more;
}
Well it works but it's dirty and I hate duplicating code, not mentioning the slightly longer page load. In case I would like to redefine .twitter-foo from my library, what can I do to avoid the bloated CSS ?
EDIT: I'm not talking about a middleware (minifier?) between SASS and CSS output but just SASS really.
What you could do is be more specific, meaning add more selectors so you can target .twitter-foo in different ways. Try giving your body tag a page id or your main element is what I usually do. So...
<body id="page1">
</body>
then in the scss you can:
#page1 .twitter-foo {
float:none;
}
OR
to override or not override add !important to the end of the style for example:
.twitter-foo {
float:none !important;
}
hope that helps.
Edit
As discussed Can the SASS minifier remove duplicate styles?
you may be able to compile your sass then run it through a css tidy which will remove duplicate classes and stuff or try out that ruby gem in the answers http://zmoazeni.github.io/csscss/.
Question
I use Paul Irish's IE Conditional Comments trick to target different versions of IE. In sass how do I apply one of these classes when nested in another class.
.container{
// I need to put a ie8 specific style here which is a .ie8 class applied to the body
}
I'd like to avoid doing this if possible (it's nice to be able to keep the properties together):
.container{}
.ie8{
.container{}
}
Is this possible?
I believe this is what you're looking for - using SASS's parent selector "&", you can do this:
.container {
.ie8 & {
// ie8 specific styles here
}
}
I am a little unclear as to what you are trying to do specifically. But If you are trying to do what I think you are trying to, then you could use a variable.
For example, lets say you only want to have your font color red in IE. You could do something like this.. Although I don't see how using SASS would be all that beneficial in this use case, unless of course you are trying to do something different.
SASS:
You can test this at: http://sassmeister.com/
$ieEightAndNine: "\0/";
.container {
color:unquote(red + $ieEightAndNine);
width:100px;
height:100px;
}
CSS:
.container {
color: red\0/;
width: 100px;
height: 100px;
}
TEST IN CHROME VS IE:
http://jsfiddle.net/3G48v/
I was wondering if it is possible to define the styles of an element depending on the value of the body ID.
It is difficult to explain but something like this would be ideal:
HTML:
<body id="home">
CSS:
body#home {
a { /* code here */ }
p { /* code here */ }
}
body#profile {
a { /* different code here */ }
p { /* different code here */ }
}
I know I can do this:
body#home a { /* code here */ }
but that becomes very repetitive.
I will be looking forward to your responses,
Peter
You can do this if you use a CSS framework like SASS or LESS
Here's the documentation on how to do this with LESS. Hope this helps.
IDs are supposed to be unique, so #home { ... } is acceptable.
Then and child elements would be:
#home .myClass { ... }
This technique if often used to re-skin pages be simply changing the ID or class on a body.
Be aware that while nesting styles like this can be supported using CSS frameworks, it should be well thought-out to maintain modularity and clean inheritance in your CSS. You can end up doing more harm than good. In particular, watch out for something know as the inception rule, described here:
http://thesassway.com/beginner/the-inception-rule
The Inception Rule: don’t go more than four levels deep.
Any change you make to your markup will need to be reflected into your
Sass and vice versa. It also means that the styles are bounded for
life to the those elements and that HTML structure which completely
defeats the purpose of the "Cascade" part of "Cascading Style Sheets."
If you follow this path, you might as well go back to writing your CSS
inline in your HTML (please don't).
The best way to do what you are talking about is to have a base stylesheet the site.
They have either:
A <style> element in the header overriding anything you choose
or
Have a different stylesheet for each page
I remember reading about a Sass feature that allowed you to specify a list of elements and then a child and it would compile to a list of multiple selectors. I ahve searched around but can't find it.
I want it to compile down to this:
header .container,
footer .container
background: yellow
But i'm sure there is a feature of Sass that allows writing that in a much nicer way.
Any ideas?
That style could be refactored as this:
.container {
header &, footer & {
background: yellow;
}
}
But maybe you are thinking of a Compass feature? http://compass-style.org/reference/compass/helpers/selectors/#nest
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.