I am building websites for a while, and I have a question about CSS I can't really rid over. So there is that frequent situation when multiple classes affect a DOM element, and both classes declare the same properties. For example:
.first {
color:white;
}
.second {
color:black;
}
I know that if I have an element with class="first second" in that the text will be black. If I rather want it to be white, I have several options:
Using !important: I know this one is handy and I use it, but sometimes, if I use it too often, my CSS may become messy. I mean, multiple !important's can result the same basic situation.
Reordering the classes inline: if I am correct, which class comes first, it will be the priority one. This is nice, but i often work with environments where I can't affect that. Secondly, this is not a global but a local solution.
Reorder the CSS itself: well, this sounds interesting, but if I work with many stylesheets (and I do), it is hard to track, especially when it is WIP.
Actually what I am looking for is some workaround like z-index but for priorizing which class is stronger. Because I can't really find anything useful in this topic, I am just curious maybe it is a user error, and you guys know something I don't. How do you manage this? What do you suggest?
class="first second" is the same as class="second first". The priority is based on the position of the declarations in your css and not in their position on the html element.
So, if you want priority of a class against another, put the top priority class LAST on the css file.
.first {
color:white;
}
.second {
color:black;
}
in this example, class second has always priority over class first. This happens because browser scans through the css top-to-bottom and always applying the rules of matched classes that finds. So, the last matched class has priority over the previous matched classes.
see this fiddle: http://jsfiddle.net/5c29dzrr/
At the same specificity level, the CSS selector that is furthest down the stylesheet will be applied. So in your example, if you wanted in that situation to have the element with the white colour you would have to order your properties like so:
.second {
color: black;
}
.first {
color: white;
}
The order of the classes in the HTML tag is not important; it is the order in which they appear in your CSS.
The better way to handle this is to go with some better naming convention such as BEM or SMACSS so that you don't have the issue of conflicting class names.
Edit: It might be worth reading up on specificity and the cascade for a better understanding of this. I found this calculator to be pretty handy in determining which rules will take precendence, although these days you can just use the developer tools to find out that information.
Related
So, I'm not sure what I've stumbled upon here. I'm working with some CSS and I know it is common place to do something like this:
#content{
/* Style the content div. */
}
#content p{
/* Style all p elements in the content div. */
}
I'd like to give one specific p element a float:right style. Only one such p element will occur in the content element. Naturally, I'd just give this element an id, but then I had the idea to do it this way:
#content #right_floating_p{
float:right;
}
This works when I run the code, but I was wondering about best practice and whether or not this actually does anything scope wise. I could just as easily define a separate id for right_floating_p, but to me it feels natural that it should be defined with the content id because it will be used only on one p element inside the content element.
If anyone has any information about this syntax, please let me know. Thanks!
My recommendation is to only include the last ID. This is fairly standard separation of concerns. What if you want to change the first ID #content, but the last one #right_floating_p still makes sense and shouldn't change? There is more room for error if you specify something unnecessarily.
Other reasons this is good:
Smaller, faster (but barely) download size for your users.
More readable, in my opinion.
Faster (but barely) performance.
Over-qualifying tags is bad practice in general, as far as performance goes. Browsers read your selectors from right-to-left, by the time it interprets your #content selector, that information is pointless. My advice is to not trust that the browser will optimize for this.
Alvaro nailed it in his comment above.
The id must be unique on the page, but not necessarily across the whole site. So, for instance, if you had the #right_floating_p element on every page, but it had a #content element as an ancestor only on a certain page where you wanted it styled differently, then you'd want to use the #content #right_floating_p selector to apply the context-specific style.
I would suggest only using the most precise selector as you can, not only for readability and file size, but also for specificity.
CSS selectors have a specificity to them, so if you were to override it later (such as with a media query), the more specific selector will override the less specific one.
#content #right_floating_p {
color: red;
}
div #right_floating_p {
color: green; /* Will not apply, as it's less specific */
}
p {
color: black; /* Even less specific */
}
It will work having the first selector, but it's not necessary.
I'm trying to be more modular in my CSS style sheets and was wondering if there is some feature like an include or apply that allows the author to apply a set of styles dynamically.
Since I am having a hard time wording the question, perhaps an example will make more sense.
Let's say, for example, I have the following CSS:
.red {color:#e00b0b}
#footer a {font-size:0.8em}
h2 {font-size:1.4em; font-weight:bold;}
In my page, let's say that I want both the footer links and h2 elements to use the special red color (there may be other locations I would like to use it as well). Ideally, I would like to do something like the following:
.red {color:#e00b0b}
#footer a {font-size:0.8em; apply-class:".red";}
h2 {font-size:1.4em; font-weight:bold; apply-class:".red";}
To me, this feels "modular" in a way because I can make modifications to the .red class without having to worry so much about where it is used, and other locations can use the styles in that class without worrying about, specifically, what they are.
I understand that I have the following options and have included why, in my fairly inexperienced opinion, they are less-than-perfect:
Add the color property to every element I want to be that color. Not ideal because, if I change the color, I have to update every rule to match the new color.
Add the red class to every element I want to be red. Not ideal because it means that my HTML is dictating presentation.
Create an additional rule that selects every element I want to be red and apply the color property to that. Not ideal because it is harder to find all of the rules that style a specific element, making maintenance more of a challenge
Maybe I'm just being an ass and the following options are the only options and I should stick with them. I'm wondering, however, if the "ideal" (well, my ideal) method exists and, if so, what is the proper syntax?
If it doesn't exist, option 3 above seems like my best bet. However, I would like to get confirmation.
First of all you cannot do apply-class:".red";
to perform this type of action i will suggest you to use this method
.red {color:#e00b0b;}
h2 {font-size:1.4em; font-weight:bold;}
.mymargin{margin:5px;}
<h2 class="red mymargin">This is h2</h2>
and to use in div
<div id="div1" class="red mymargin"></div>
In this case if you will change in .red class.it will be changed everywhere
Short answer: There's no way to do this in pure CSS.
Longer answer: Sass solves this problem via the #extend directive.
.error {
border: 1px #f00;
background-color: #fdd;
}
.seriousError {
#extend .error;
border-width: 3px;
}
This lets you keep your CSS modular in development, though it does require a precompilation step before you use it. It works very nicely though.
You can use the DOM in javascript to edit the id and/or class attributes of HTML tags dynamically.
I agree with DarthCaesar and jhonraymos. To update a class using JavaScript, all you would need is a simple:
function toggleColorClass(e){
var redClass = document.getElementsByClassName('red');
redClass.removeAttribute('class', 'red');
/*Set the class to some other color class*/
redClass.setAttribute('class', 'blue');
}
Of course, to make this work, you would need to include the above function in your document somewhere... if this is all the JS you're using you can probably stick it in the head or even use it inline. You would probably also want to write it so that the toggle goes in both directions, i.e. turning red on and off. Furthermore, jhonray's snippet is probably how you would want to mark up your CSS.
I have lots of CSS files on my current project, and a lot of the styles in these files have !important besides them. A feeling inside me tells me that this is not a good thing. Can someone shed some light on what happens when we use !important and whether it is a good idea or not.
thanks,
Sachin
!important means the rule cannot be overridden. Take note that user stylesheets using !important will override author stylesheets.
http://www.w3.org/TR/CSS21/cascade.html#important-rules
Whether this is bad or good really depends on the usage. I don't use this keyword often myself. One example is that it allows me to override styles pulled in from 3rd party widgets/plugins.
!important gives a style precedence and will ensure (where it can) that it is the style used. If you are using !important because your selectors just aren't specific, or well thought out, enough, then that's not the way they should be used. For me, there more useful for when you may have to deal with styles you have no control over.
To illustrate, where you might want to use `!important, you might have two stylesheets. One 'global' , that you have control over and one 'local', that you do.
In the global stylesheet, you might have the following:
p span {
color: black;
}
In the local one, you could override this by doing:
p span {
color: red;
}
This might work, but if the local one is included before the global one, there will be a conflict and the global styles will take precedence. To overcome this, you can do:
color: red!important;
In the case where you could just be more specific with your selectors, it would be better to do that, rather than use !important.
Global, all spans are black:
span {
color: black;
}
In local, spans inside paragraphs are red:
p span {
color: red;
}
There's nothing 'wrong' with using !important really, I guess it's a case by case scenario, but hopefully the above explains how to make the best use of them.
Some more discussion on 'When using !important is the right choice' over on CSS tricks.
Our production environment is using an adaptation technology that is incompatible with multiple css classes. This means it's easy to forget and use two classes when styling HTML, and have it break once it gets to production.
I would like to use CSS as a way to highlight when someone forgets and accidentally applies two classes to an element.
Something like this is my intent, although of course this is invalid. It should highlight any element that has two classes applied to it:
.*.* { /* not valid (I wish) */
outline:2px dotted red;
}
I understand that this would work if I knew the classes, the problem is I want to flag ANY two classes:
.classA.classB { /* not good enough */
outline:2px dotted red;
}
I understand I could do this with JS and a bookmarklet, and maybe that is the only solution. If it is possible with just CSS that would be better as it would automatically flag things for all developers and QA.
I just found an acceptable answer:
[class*=" "] {
outline:2px dotted red;
}
This highlights anything with a space in the class attribute. It gets some false positives, because sometimes spaces in a class attribute happen legitimately as a result of legible server side code, but I prefer the false positives to false negatives.
Any better ideas?
To remove most false positives (e.g. space-padded attribute values), you can use this selector:
[class*=" "]:not([class^=" "]):not([class$=" "]) {
outline: 2px dotted red;
}
This still does not filter out repeated classes in values such as class="foo foo" as pointed out by Phrogz in your own answer, but it's better than nothing, and I think that's much less likely to occur than class attributes with whitespace padding.
This is not possible using CSS alone.
And, if I may say so, your production environment is silly. CSS without multiple classes is like a tag cloud with only one tag allowed per item. It defeats some of the purpose. Fix your production environment to not abuse CSS in this manner, instead of limiting your authors from properly, semantically describing the content.
I'm currently working on refactoring a large amount of CSS, and a common trend I'm seeing is that several classes have been created for a very specific item on a page. Rather than trying to describe what they do, the classes are named things like "PressReleaseText", or "SpecLabel", etc. Most of these just define one item, like a font-size or a color.
I'm wondering if it would be better to just create several utility classes, like .fontSize140 {font-size: 140%;}, .bgColorWhite{ background-color: white;}, and utilize those in place of all the duplication occurring across the current set of classes.
Are there any drawbacks to doing this? The point where it becomes blurry is if a current class has 3 attributes set, like color, background color, and font size, and I already have generic classes for all three of those, would my class definition in the html just look something like class="white bgColorBlue fontSize140". That just seems excessive.
This is absolutely a horrible practice. It's 10x worse than the current class names that you're trying to replace. Consider the following class names:
fontSize140
bgColorWhite
marginTop150
These are obviously very descriptive class names. The problem is that they describe the styles behind the class, not the content that it styles. While this can be easier to read in HTML, it will be a complete nightmare in the future when and if you decide to make even the tiniest redesign.
For example, let's say we just applied these three classes to a block of text. It has a font size of 140%, a white background, and a top margin of 150px. That's all fine--until we decide that it needs to be 90% font, a blue background, and no top margin. Now, not only do you have to change the CSS declarations, you have to either:
(1) edit every instance of the class in the HTML to be fontSize90bgColorBlueNoTopMargin or whatever; or
(2) leave the class name alone and leave an extremely confusing class name in the HTML.
Either way it will be a massive pain for you in the future, whereas the current class names (e.g., specLabel, pressReleaseText) appropriately describe the content that they style; their styles can be easily changed without affecting the content inside of them, and thereby never affecting the name of the class.
Part of the point of CSS is to separate the content from the presentation, to make it easier to alter the presentation without altering the content. If you have class="white bgColorBlue fontSize140" all over the place, you have defeated this goal; you might as well just go with style="color: white; background-color: blue; font-size: 140%". Your classes should say what you mean not what you want it to look like.
If you find yourself repeating certain settings for lots of classes, like the following
.PreReleaseText { font-size: 140% }
.SpecLabel { font-size: 140%; background-color: white }
.SomeOtherThing { font-size: 140% }
You can instead combine several of them into one single rule
.PreReleaseText, .SpecLabel, .SomeOtherThing { font-size: 140% }
.SpecLabel { background-color: white }
If you really do just have several classes that are synonyms of each other, you might want to think about why that is. Why are all of those styled the same way? Is there some class name you can come up with that encompasses all of those uses? Or is it just incidental that they happen to be styled the same way? If it's just incidental, then they should have separate rules, so you can easily update the styles of each class independently. If there is some unifying theme, then perhaps you should merge them into a single class.
Remember to consider what will happen in different media, or in a redesign. Imagine that the company is bought out, and you want to change the color scheme to match the new corporate colors, without doing a full redesign. If you have a .bgColorWhite class, but only some of the things labelled with that class should change to a new color in the redesign, you'll have to go through all of your templates and markup again to separate out the classes, but if you labelled them with more meaningful classes, you may be able to just tweak the colors in the appropriate classes.
These are some general guidelines; you should always use what works best for you. If you had a more specific example, I might be able to suggest a better way of refactoring your classes for your specific need.
There is not a right and wrong way to do this as far as I'm concerned. It depends on knowing how often you'll reuse things and what makes it easiest to understand the CSS. I've often seen those general things like .fontSize140 end up causing problems later on when you have to make changes. I prefer in most cases to group classes but keep the individual names.
So I might have
.Thing1,
.Thing2,
.Thing3 { font-size:14px; }
.Thing1 { font-weight:bold; }
.Thing2 { font-size:italic; }
Instead of having
.font14 { font-size:14px; }
And then still needing the .Thing1 and .Thing2 clases.
That was I can always change the CSS easily later without having to worry what is sharing that common .fontSize140 for example.
I would stay away from getting too general like .fontSomeSize. That said i generally try and use classes that define things as logical "types" or "objects" for example .ruled-list or .summary.
Why don't you try something like this:
Use a css preprocessor like sass.
/* define app/website colors */
$main-color: #223c61;
$secondary-color: #2954a2;
$accent-color: #4cceac;
/* some example css classes */
.text-main { color: $main-color; }
.bg-secondary { background-color: $secondary-color; }
.bg-accent { background-color: $accent-color; }
/* define app/website spacings */
$spacing-xs: 10px;
$spacing-sm: 15px;
$spacing-md: 25px;
$spacing-lg: 35px;
/* some example css classes */
.padding-up-xs { padding-top: $spacing-xs; }
.padding-down-lg { padding-bottom: $spacing-lg; }
.margin-left-md { margin-left: $spacing-md; }
The above code has generic css classes, but it is not bound to a specific value. For some very specific styling, you can always make a custom css file to account for that.
I see a lot of people using custom margins and paddings throughout their css. See the code below.
.blog-post-sidebar-right { margin-top: 14px; }
.news-post-bottom-text { margin-bottom: 23px; }
As a rule of thumb, I always use 4/5 predefined margins and paddings. And not some arbitrary number you make up on the fly.
So why not define generic css classes to use them. I took this same idea an applied it to all of my css. Now I can have the same code base in every project.
Because you now use a css preprocessor, it's easy to maintain, flexible and easy to extend.
Im not saying this is the best option, but it does the job for me.