I know CSS selector with the highest specificity takes precedence (i.e. .classname < #idname).
I also know that if things are the same specificity, then the last statement called takes precedence:
.classname1 { color: red; }
.classname1 { color: blue; } // classname1 color will be blue
Does the ordering of HTML classes on a DOM element affect the statement priority?
I have to disagree slightly with Jon and Watson's answers, as...
Yes, it Can (depending on the statement)
Your question is:
Does the ordering of CSS classes on a DOM element affect the statement priority?
Which does depend on the statement in question.
HTML Ordering Does Not Typically Matter
The following are equivalent when it comes to a straight call to a class (i.e. .class1 or .class2) or to a combined call (i.e. .class1.class2 or .class2.class1):
<div class="class1 class2"></div>
<div class="class2 class1"></div>
Cases Where Statement Priority for above HTML Can be Affected Based on HTML Order
The main place where ordering in HTML matters is with the use of attribute selectors in your CSS.
Example 1 Fiddle using the following code seeking to match attribute value will NOT have any change in font color, and each div will have different properties because of the ordering of the classes:
[class="class1"] {
color: red;
}
[class="class1 class2"] {
background-color: yellow;
}
[class="class2 class1"] {
border: 1px solid blue;
}
Example 2 Fiddle using the following code seeking to match beginning of attribute value will NOT have any change in font color for the second div, and each div will have different properties because of the ordering of the classes:
[class^="class1"] {
color: red;
}
[class^="class1 class2"] {
background-color: yellow;
}
[class^="class2 class1"] {
border: 1px solid blue;
}
Example 3 Fiddle using the following code seeking to match end of attribute value will NOT have any change in font color for the first div, and each div will have different properties because of the ordering of the classes:
[class$="class1"] {
color: red;
}
[class$="class1 class2"] {
background-color: yellow;
}
[class$="class2 class1"] {
border: 1px solid blue;
}
A Clarifying Statement about "Priority"
To be clear, in the cases above, what is affected as far as "statement priority" is concerned is really a matter of whether the statement actually applies or not to the element. But since the application or not is in a sense, the basic priority, and since the above are cases where such application is actually based on the ordering of the classes on the HTML Dom element (rather than the presence or absence of the class), I thought it worth adding this as an answer.
Possible Valid Use of Class Ordering?
This is a thought occurring to me, based on BoltClock's comment. Consider just two classes being used to style elements based on whatever factors are deemed critical to different styling. These two classes theoretically can replace the use of eleven different individual classes using the combination of attribute selectors (actually, as will be noted later, the possibilities are almost limitless with but a single class, but I'll discuss that in a moment since this post is about ordering of multiple classes). For these two classes we can style elements differently as follows:
Assuming these HTML Combinations
<div class="class1">Element 1</div>
<div class="class2">Element 2</div>
<div class="class1 class2">Element 3</div>
<div class="class2 class1">Element 4</div>
CSS Possibilities
/* simply has the class */
.class1 {} /* affects elements 1, 3, 4 */
.class2 {} /* affects elements 2-4 */
/* has only a single class */
[class="class1"] {} /* affects element 1 only */
[class="class2"] {} /* affects element 2 only */
/* simply has both classes */
.class1.class2 {} /* affects elements 3-4 */
/* has both classes, but in a particular order */
[class="class1 class2"] {} /* affects element 3 only */
[class="class2 class1"] {} /* affects element 4 only */
/* begins with a class */
[class^="class1"] {} /* affects elements 1 & 3 only */
[class^="class2"] {} /* affects elements 2 & 4 only */
/* ends with a class
NOTE: that with only two classes, this is the reverse of the above and is somewhat
superfluous; however, if a third class is introduced, then the beginning and ending
class combinations become more relevant.
*/
[class$="class1"] {} /* affects elements 2 & 4 only */
[class$="class2"] {} /* affects elements 1 & 3 only */
If I calculate right, 3 classes could give at least 40 combinations of selector options.
To clarify my note about "limitless" possibilities, given the right logic, a single class can potentially have imbedded in it code combinations that are looked for via the [attr*=value] syntax.
Is all this too complex to manage? Possibly. That may depend on the logic of exactly how it is implemented. The point I am trying to bring out is that it is possible with CSS3 to have ordering of classes be significant if one desired it and planned for it, and it might not be horribly wrong to be utilizing the power of CSS in that way.
No, it does not. The relevant part of the W3C standard makes no mention of the order of appearance for classes.
No, it does not, like you said, if two rules have the same specificity, the one that comes later in your CSS will be applied.
No. But if you want to make one of your declaration blocks to has more precedence (w/o many !importants) make its selector more specific.
For example, for a div:
div.classname1 { color: red; } /* classname1 color will be red (for `div`s) */
.classname1 { color: blue; }
What's missing or a little hard to find in other answers is this:
What matters is the order in which the browser reads/parses the class names
The class defined last will win
.a {
color: red;
}
.b {
color: blue;
}
<div class="a b">This text will be blue</div>
<div class="b a">This text will ALSO be blue</div>
Example comes from this source
May be affected by the order of your imports
Because if this you may need to pay attention to how you import CSS in your files.
For example in my JavaScript based project I have a component that I can pass extra classes to. In order for my own classes to overwrite styles of the classes of the component itself I need to first import the component I wish to style (which will import its own styles) and only then import my own styles:
//import the component first, which will import css
import {SomeComponent} from 'some-library/SomeComponent';
//And THEN our own styles
import './styles.css';
return <SomeComponent className={myClassName} />
Like this my buildprocess (Webpack) will put my own classes later in the CSS bundle than the components ones.
Related
I know CSS selector with the highest specificity takes precedence (i.e. .classname < #idname).
I also know that if things are the same specificity, then the last statement called takes precedence:
.classname1 { color: red; }
.classname1 { color: blue; } // classname1 color will be blue
Does the ordering of HTML classes on a DOM element affect the statement priority?
I have to disagree slightly with Jon and Watson's answers, as...
Yes, it Can (depending on the statement)
Your question is:
Does the ordering of CSS classes on a DOM element affect the statement priority?
Which does depend on the statement in question.
HTML Ordering Does Not Typically Matter
The following are equivalent when it comes to a straight call to a class (i.e. .class1 or .class2) or to a combined call (i.e. .class1.class2 or .class2.class1):
<div class="class1 class2"></div>
<div class="class2 class1"></div>
Cases Where Statement Priority for above HTML Can be Affected Based on HTML Order
The main place where ordering in HTML matters is with the use of attribute selectors in your CSS.
Example 1 Fiddle using the following code seeking to match attribute value will NOT have any change in font color, and each div will have different properties because of the ordering of the classes:
[class="class1"] {
color: red;
}
[class="class1 class2"] {
background-color: yellow;
}
[class="class2 class1"] {
border: 1px solid blue;
}
Example 2 Fiddle using the following code seeking to match beginning of attribute value will NOT have any change in font color for the second div, and each div will have different properties because of the ordering of the classes:
[class^="class1"] {
color: red;
}
[class^="class1 class2"] {
background-color: yellow;
}
[class^="class2 class1"] {
border: 1px solid blue;
}
Example 3 Fiddle using the following code seeking to match end of attribute value will NOT have any change in font color for the first div, and each div will have different properties because of the ordering of the classes:
[class$="class1"] {
color: red;
}
[class$="class1 class2"] {
background-color: yellow;
}
[class$="class2 class1"] {
border: 1px solid blue;
}
A Clarifying Statement about "Priority"
To be clear, in the cases above, what is affected as far as "statement priority" is concerned is really a matter of whether the statement actually applies or not to the element. But since the application or not is in a sense, the basic priority, and since the above are cases where such application is actually based on the ordering of the classes on the HTML Dom element (rather than the presence or absence of the class), I thought it worth adding this as an answer.
Possible Valid Use of Class Ordering?
This is a thought occurring to me, based on BoltClock's comment. Consider just two classes being used to style elements based on whatever factors are deemed critical to different styling. These two classes theoretically can replace the use of eleven different individual classes using the combination of attribute selectors (actually, as will be noted later, the possibilities are almost limitless with but a single class, but I'll discuss that in a moment since this post is about ordering of multiple classes). For these two classes we can style elements differently as follows:
Assuming these HTML Combinations
<div class="class1">Element 1</div>
<div class="class2">Element 2</div>
<div class="class1 class2">Element 3</div>
<div class="class2 class1">Element 4</div>
CSS Possibilities
/* simply has the class */
.class1 {} /* affects elements 1, 3, 4 */
.class2 {} /* affects elements 2-4 */
/* has only a single class */
[class="class1"] {} /* affects element 1 only */
[class="class2"] {} /* affects element 2 only */
/* simply has both classes */
.class1.class2 {} /* affects elements 3-4 */
/* has both classes, but in a particular order */
[class="class1 class2"] {} /* affects element 3 only */
[class="class2 class1"] {} /* affects element 4 only */
/* begins with a class */
[class^="class1"] {} /* affects elements 1 & 3 only */
[class^="class2"] {} /* affects elements 2 & 4 only */
/* ends with a class
NOTE: that with only two classes, this is the reverse of the above and is somewhat
superfluous; however, if a third class is introduced, then the beginning and ending
class combinations become more relevant.
*/
[class$="class1"] {} /* affects elements 2 & 4 only */
[class$="class2"] {} /* affects elements 1 & 3 only */
If I calculate right, 3 classes could give at least 40 combinations of selector options.
To clarify my note about "limitless" possibilities, given the right logic, a single class can potentially have imbedded in it code combinations that are looked for via the [attr*=value] syntax.
Is all this too complex to manage? Possibly. That may depend on the logic of exactly how it is implemented. The point I am trying to bring out is that it is possible with CSS3 to have ordering of classes be significant if one desired it and planned for it, and it might not be horribly wrong to be utilizing the power of CSS in that way.
No, it does not. The relevant part of the W3C standard makes no mention of the order of appearance for classes.
No, it does not, like you said, if two rules have the same specificity, the one that comes later in your CSS will be applied.
No. But if you want to make one of your declaration blocks to has more precedence (w/o many !importants) make its selector more specific.
For example, for a div:
div.classname1 { color: red; } /* classname1 color will be red (for `div`s) */
.classname1 { color: blue; }
What's missing or a little hard to find in other answers is this:
What matters is the order in which the browser reads/parses the class names
The class defined last will win
.a {
color: red;
}
.b {
color: blue;
}
<div class="a b">This text will be blue</div>
<div class="b a">This text will ALSO be blue</div>
Example comes from this source
May be affected by the order of your imports
Because if this you may need to pay attention to how you import CSS in your files.
For example in my JavaScript based project I have a component that I can pass extra classes to. In order for my own classes to overwrite styles of the classes of the component itself I need to first import the component I wish to style (which will import its own styles) and only then import my own styles:
//import the component first, which will import css
import {SomeComponent} from 'some-library/SomeComponent';
//And THEN our own styles
import './styles.css';
return <SomeComponent className={myClassName} />
Like this my buildprocess (Webpack) will put my own classes later in the CSS bundle than the components ones.
This question already has answers here:
Is there a CSS selector by class prefix?
(4 answers)
Closed 8 years ago.
Twitter Bootstrap's different column selectors have different CSS properties. Col-md-1 has a smaller width than col-md-2. However, they all have some properties in common.
How can one rule be created that applies to multiple classes who all share the same prefix?
I imagine something like this:
.col*{
margin:0,2%;
}
.col-md-1{
width:4.3333333333%;
}
.col-md-2{
width:6.33333333%;
}
In the example above, both of .col-md-1 and .col-md-2 would have a margin of 0,2%. What is the correct way (if any) of doing this?
You can use :
[class^=col] {margin:0.2%;}
div {
height: 50px;
margin: 10px;
}
[class^=col] {
background: red;
}
<div class="col-md-1"></div>
<div></div>
<div class="col-md-2"></div>
This ^= means "begins with". You could also use the [class*=col] or [class*=md] for more info, see the specs on substring matching attribute selectors.
(Note that you should be using a dot instead of a comma or a white space in the margin value declaration)
You can either use a ^= operator (starts with), or a |= operator (is on a dash-separated list):
[class^=col] {
/* this will work just for prefixes */
}
[class|=col] {
/* this will work for any dash-separated segment... */
}
[class|=md] {
/* ...such as "md" in your case */
}
A word of warning, though - these aren't the best selectors in terms of performance. Try not to use them extensively.
My question is different than this one, but it's regarding the same principle, so this quote is relevant here too:
from https://github.com/stubbornella/oocss/wiki
Essentially, this means “rarely use location-dependent styles”. An object should look the same no matter where you put it. So instead of styling a specific h2 with .myObject h2 {...}, create and apply a class that describes the h2 in question, like h2 class="category".
But what if the design dictates that an object's style changes when it's inside certain containers? Here's a simplified example of my problem. Let's say there's an object called foo, and a container object called bar. foo and bar have their own location-independent styles:
.foo {
...
}
.bar {
...
}
But when foo is inside container bar like so, its color needs to change when the user hovers over bar:
<div class="bar">
...
<div class="foo">
...
</div>
...
</div>
It seems in this case, you can't avoid writing a location-dependent selector that looks like this:
.bar:hover .foo {
// color style
}
One solution I thought of is to introduce a class that's explicitly dependent on bar (named using BEM naming convention to be explicit about parent-child relationship), and add it to the foo object:
<div class="bar">
...
<div class="foo bar__foo">
...
</div>
...
</div>
.bar:hover .bar__foo {
// color style
}
I want to confirm, is this a good way to handle the issue? Are there other ways in OOCSS as well?
The big concern here isn't that your chaining classes together, it's that your classes are location independent. Nesting is going to happen. Approaches like OOCSS are great because they help to you know when things like nesting and class-naming is going awry.
Mark Otto released a Code Guide last week and here are some relevant points:
Keep selectors short and strive to limit the number of elements in each selector to three.
Scope classes to the closest parent only when necessary (e.g., when not using prefixed classes).
He also provides these examples:
/* Bad example */
span { ... }
.page-container #stream .stream-item .tweet .tweet-header .username { ... }
.avatar { ... }
/* Good example */
.avatar { ... }
.tweet-header .username { ... }
.tweet .avatar { ... }
In short: Aim to scope a class to it's parent. Don't go further than 3 selectors.
You're fine going with:
.bar:hover .foo { ... }
Further Reading
Stop The Cascade
Scope CSS Classes with Prefixes
I'm wondering how can I apply a style to EVERY h2 that DOES have ANY any class attached to it, thus having the effect that the style will NOT be applied on a plain h2..eg..
<h2 class="1"></h2>
<h2 class="2"></h2>
<h2 class="3"></h2>
<h2 class="a"></h2>
<h2></h2>
All the ones with a class should have a style - and just plain h2 should not, (This is a huge site with hundreds of styles)...so any easy way to do this?
There is a method to do it but it's only possible with browsers that support CSS3 :not pseudo class.
h2[class] {
/* Styles for <h2> with a class, regardless of the value */
}
h2:not([class]) {
/* Styles for <h2> without classes */
}
I hope it works!
[Edit] I've made a simple demo for you here - http://jsfiddle.net/fL2sT/
What you're asking for is how CSS works by default.
The correct way to style elements which have no specific class assigned to them is to style the base element, as Ahsan demonstrated above. I don't know why he got downvoted.
h2 { property: value; }
Note that if H2 elements do have classes assigned to them, then that styling may override your base style.
So if you have: h2 { color:#333; font-size:2em; } as your base style, and then apply class="myClass" to it where: .class { color: #000; }, then the base style's color will be overriden (but not the font size). This is the cascade in Cascading Style Sheets.
Another way is to target them conditionally:
div#nav h2:first-child { property:value; }
which gives you contextual control, but again, class assignment will always override base styling, and may also override context targeting if the class application has higher specificity.
Why not simply use
h2[class] { ... }
I've read several tutorials on CSS, but none of the sites I've looked at mentions or explains what a "." means in CSS.
What does the . mean?
Nothing without context.
I'll hazard a guess that you are referring to a class selector.
Well, in the following context:
.foo {
//properties
}
it indicates that foo is a class. A # means it's an id and if it has nothing it means that it is for all tags of that type. So, in html, you would implement something with a "." like this:
<div class = "foo"></div>
For a "#" it would be
<div id = "foo"></div>
Use class/"." if you want to apply it to more than one thing. Use id/"#" if you want it to apply to one thing.
Ok, so if your wondering what a class is:
A class is one of the three (I think it's 3) types of ways you select stuff in css. The id (which I explained) says that the following properties apply to anything (usually one thing) with 'id="foo"' in its tag. A class selector means that it applies to everything with a "class="foo"" in its tag. If it has none of these than it means that it applies to all things with that name.
.foo { //applies to all things with "class="foo"" in tag.
border: black thin solid // applies a black border to them.
}
#foo { //applies to all things with "id="foo"" in tag.
border: black thin solid // applies a black border to them.
}
div{ //applies to all div tags.
border: black thin solid // applies a black border to them.
}
h1{ //applies to all h1 tags
border: black thin solid // applies a black border to them.
}
It is a class selector. Means the rule should be applied to all elements that have an attribute class with the value after the ..