What are the benefits of changing particular bits of style inline in the HTML or changing it from an external stylesheet using Javascript?
For instance, this post explains how one can accomplish changing styles from an external stylesheet. However, the process seems to be much more complicated than changing it inline, and it also refers there may be cross-browser problems. However, the post may be outdated (it is 3 years old, and one of the comments says even then it was 4 years old). Is there another more recent way of doing this?
I ask this because I try to keep my HTML and CSS completely separate.
However, is it maybe simpler, in terms of legibility and performance of the code, to simply specify the styles I want to change inline rather than on an external stylesheet?
Are there any best practices in regard to this matter?
When temporarily accessing or modifying an element's style using Javascript, there is no difference involved in whether that style was defined inline or in css - you will get the style that is applied by precedence and Javascript changes will override any declared style.
However, general best practice is to have a separate stylesheet (or maybe several if you intend to have conditional stylesheets for IE9 and below, or to split up lots of styles into manageable chunks)
This method is less complicated when it comes to debugging and changing styles in real time.
With external stylesheets you can change the entire site in seconds by dropping a new .css file in place. You can't do that with inline styles.
There are no benefits from inline-css except that it will be given more importance.
External css have the benefits of being cached.
However while rendering the below is the order followed.
Inline CSS styles are given more importance than to styles declaredd in <style></style> and styles declared in <style> is given more importance than to styles declared in external css. files.
Inline-css and even <style> is not preferred and is generally bad practice as extra bytes are transmitted over HTTP and they cannot be cached as external css files can be.
Styling using javascript should be just up to adding a class or removing a class or hiding and showing them, to improve the user experience.
Related
I am a beginner web-designer. I know the basics of HTML, CSS and Javascript. I know that CSS used to style HTML docs, but is that the only way ? Can I use JavaScript to style HTML, somehow ? Or Is there any other way rather than CSS ?
JavaScript is a scripting language, not a styling language. While you can use JavaScript to apply CSS, it's still CSS, not JavaScript, that's defining the styles.
There exist HTML presentational attributes from a long time ago, but those have been superseded by CSS. You can still use them, not that you would want to, considering they'll most likely get translated to CSS anyway.
There also exist CSS preprocessors with custom languages, such as Sass/SCSS, LESS and Stylus, but they all compile to CSS as well, because that's what's actually implemented by browsers. So even if you use these preprocessors, at the end of the day you're still "writing" CSS.
I know that CSS used to style HTML docs, but is that the only way ?
It is the only sensible way
Can I use JavaScript to style HTML, somehow ?
You can generate CSS with JavaScript. (Not advisable for general styling).
You can use JSSS if you're only targeting Netscape 4.x.
You're also able to style HTML with HTML-attributes itself, but this way is pretty impractical and old-fashioned. Most of these techniques are deprecated and the functionality is VERY limited.
I suppose the correct answer to your question is no, because html includes some basic style elements itself. But CSS is the best way to style your documents and you absolutely should learn and use it. Once you're comfortable using CSS, try using a framework such as Twitter bootstrap to make your life easier.
It's not the only way but the recommended way.
You can include styling in your html tags but it becomes messy.
That's why CSS was invented so use it !
As mentioned previously, CSS is not the only way to stylize HTML but definitely the standard. If you're looking for a more programmatic way utilizing JavaScript you can look into less which (taken directly from the webpage) ...extends CSS with dynamic behavior such as variables, mixins, operations and functions and functions map one-to-one with JavaScript code, allowing you to manipulate values however you want.
I am considering replacing a number of static css files with style tags dynamically generated from JavaScript. My purpose is not to build a stylesheet for the whole document, but rather to use it for plugins that get added to the page, like tabs, slideshows, etc. The stylesheets I currently deal with have 10 to 20 lines.
I see several benefits:
load only a js file instead of both js and css
ability to define theming on the fly (e.g. enter colors as variables)
ability to define selectors on the fly (e.g. namespaced class names)
add browser specific styles
What would be the drawbacks of this approach? Could you recommend any good references on this topic?
I did some research and found the following tools:
less - but still requires to load a separate stylesheet
DiceJS (apparently a new library)
Less is absolutely awesome, I don't think you should try to generate css with a custom library in javascript. It's a good idea to keep your javascript as separate as possible from your css.
We use certain element class="" attributes to trigger javascript logic, but they never overlap with classes used in our less styles. (we use different casing rules for both to prevent overlap from happening).
There's also not that much benefit to dynamically load parts of your css. We have the less.js javascript running during development, but we run the 'lessc' compiler for production so we always have 1 stylesheet (and also compressing it with YUI Compressor).
Unless the total css is absolutely humongous, we prefer to load in 1 big css file at the first hit, and afterwards have the file cached.
Making sure all your css is loaded at all times (and not just parts) also helps you enforce that there are no conflicting rules. This will really benefit you if you ever must to refactoring and parts of your application move to other urls (where all of a sudden overlap becomes visible).
So I'd suggest, rather than trying to solve your issue by dynamically generating the styles you need, you may just need better organization for your css.
If you're looking for a great example of effective use of less, check out Twitter Bootstrap
Another benefit would be that each additional asset that is loaded in the page slows down the overall page load because a browser is typically only loading 4 assets simultaneously at a given time.
However, doing all of that combining on page load is likely to cause the page to slow down just as much from the processing alone... depending on how many things it needs to iterate through to make up the final css block.
In terms of performance, it seems very unlikely to me that javascript is going to elegantly / efficiently replace the styles that would've been included in a combined css file.
The other thing is that in production environments, you also can do another option which is to use a library to pre-generate a set of minified, optimized, (and obfuscated in the case of JS) code and then have 1 js file and 1 css file loaded at the time of page load, which in-turn you'd cache for speed/loading benefits. Boilerplate lib has a script for this i think.
End of the day: energy is neither created nor destroyed -- your optimizations in one place and hurt you elsewhere if you're not careful.
Using JavaScript for CSS sounds a bit messy, in my opinion. As you mention your self, I would instead recommend you to use LESS or SASS or similar. Yes, it would cause one extra resource to be loaded, but I think that is well worth it compared to using JavaScript for styling. In my opinion, it is the wrong tool for the purpose.
I want to apply ALL the CSS styles 100% with JQuery/JavaScript
But is is bad idea to do this?
Why would you create that overhead in javascript when straight HTML/CSS is fully capable of handling it? (in fact intended to)
Also, you're adding an unnecessary requirement to the styling of your site: having javascript enabled.
Main reason IMHO: Performance! Native CSS is much faster than JS.
Also worth mentioning:
Doesn't work for users with NoScript etc.
Overhead. Not such a big deal i think. There are more important things to optimize.
If you lazy load stuff, e.g. by using jQuery.load(), you have to reapply your styles to these elements. Not nice :/
Conclusion: CSS is made for styling, JS isn't.
If your visitor has javascript disabled, they'll see an ugly white page without any styling.
I don't see why you would do this, to be honest. It's not user-friendly.
Use a stylesheet.
A lot of people say to apply classes not individual styles.
You will see varying levels of performance degradation across different browsers. It's faster and cleaner to let the application render the styled HTML page because that's what it's optimized to do.
If you're dynamically loading content and already have fade effects/transitions so your content is only revealed after it's styled, you might be ok.
if you are going to do this, only apply styles with jQuery (rather than using javascript) to maintain cross-browser compatibility.
I would recommend against your approach because of the time it will take jQuery to loop through all of your elements and apply styles.
something like $('span').css(...); has to traverse the entire DOM and loop through a collection of elements. $('#title').css(...); does not have to loop through the entire DOM because it immediately knows where to look.
Also, browsers are designed to process stylesheets and render your styled elements very quickly.
I have created a Javascript based element that can be embedded into websites. The Javascript itself adds the HTML code into a pre-defined HTML container and dynamically loads the necessary CSS file that contain the element's visual definitions.
The problem starts when the site itself has its own definitions for general items. For example: The site's CSS defines a certain list style which is applied on the element's list because the element's CSS doesn't define an explicit list style or if the site's CSS overrides the element's CSS definition.
For the time being, I was able to solve this specific issue by explicitly defining the list's style and adding the !important definition. However, I would definitely want to go for a more robust solution that will assure that:
1. CSS definitions from the site's CSS that are not explicitly defined in the element's CSS will not be applied on the element
2. I will not need to explicitly add the !important definition to every one of my CSS definitions
Is there a general way in which I can specify that a site's CSS will not be applied on a certain element or that only a certain CSS will be applied to a specific element?
Any help will be greatly appreciated.
You need to use a localised reset.
Grab an existing CSS reset, such as Eric Meyer's Reset Reloaded and namespace all the selectors with your parent element, e.g. #something a { ... }.
I was going to put up the same answer as Alex, but he beat me - but I was also going to add:
If you're not going to use #alex's suggestion then ultimately you have to explicitly style all of your elements the way that you want them to appear; using selectors that keep your styles local too (and don't interfere with the parent site) - in the same way that the localised reset is suggested.
Update
Or you could do what Google Translate and many other widget-type things do, usually a no-no but in dynamic scenarios I think perfectly acceptable; since the visual style of your elements is not just important to you but to the container site: use inline styles.
Final update
So I thought I'd just double check what Google Translate does. And of course it's an iFrame inject in addition to using inline styles. They no doubt use inline styles to maximise compatibility and so that the browser doesn't have to make another request to get the stylesheet; and they would be using an iFrame so they can ensure a consistent look and feel.
Consider both of those points in tandem - and weigh that up against the amount of work that might be required in resettting all the styles for a minority portion of the page; or defining rules for every CSS property you need to control - which, let's face it, is basically all visual CSS properties.
The iFrame solution actually seems to offer the best solution - if you can use it; hence I've +1'd the first comment by #roberkules on your question.
I'm relatively new to client-side programming coming from the PHP/MySQL environment. I understand the roles both CSS and JavaScript can play in the browser environment, however, it appears CSS is irreversibly stagnant without JavaScript. I by no means want to create a debate but this is what the situation looks like to me, the "novice." So why not just use only JavaScript to set element attributes/properties? And if so, is this a common practice? (I'm sure CSS is much faster...)
Some general points:
CPU Cost
Running Javascript to apply styles to individual elements will incredibly slow. Javascript is synchronous, so it'll have to update one style at a time. Plus, as mentioned elsewhere, traversing the DOM is computationally expensive. More so if you're applying styles since you're forcing the browser to re-render the site each time you apply a change.
Brain Cost
It's also mentally expensive to try to write and maintain styles in Javascript. It's a functional language never intended to contains the rules of layouts. CSS is just a lot easier to read.
They Cascade!
CSS stands for Cascading Style Sheets. One of the great benefits styles can inherit properties from eachother. Consider the following:
a.nav { font-weight: bold; }
Now all your links with a class of "nav" are bold. But should you wish to further modify a link you'll still be able to:
li a.nav { color: red; }
Now all your a.nav links contained within a list item will be red and bold. It's possible to do this is javascript, but you'd have to force it and maintenance would be horrible.
If you use Javascript for styles your coworkers will beat you to death!
I think this one kind of speaks for itself
Css is for page layout and style.
Javascript is for behavior.
Even if it is possible to completely replace css with javascript, it's not considered standard practice and would be frowned upon severely by most web developers.
Good web development always assumes that a client may have javascript turned off and will provide for a graceful default setting. Replacing css with javascript may make this impossible.
It is far from a common practice, in fact it would probably be viewed as a bad practice!
CSS is used to set the styles of the page and it is rendered when the page loads. Javascript comes into play after the page loads and can manipulate the existing styles and page.
If you were to put it into all JS it would be hugely inefficient! DOM manipulation gets expensive if you do it a lot in JS, and doing all styles in javascript instead of CSS would be lots of manipulation. The load on the client would be ridiculous and there would probably be a noticeable lag in the client as it tried to make all those changes. Plus what happens if a client has javascript disabled? There goes your entire site's look and feel.
Think of CSS as defining how the page looks and should be rendered, and then think of JS as changing that page after it's done rendering. You shouldn't push anything into a javascript that you can do with a simple CSS style up-front.
The real problems with changing out your CSS for javascript would be maintainability and performance. CSS makes it very simple to find a single elements styling, and change it, without effecting the rest of your page. Javascript would become cumbersome at best for even a simple page, and completely unmanageable for a more complex page.
On the performance side, any time javascript is executing, your page will "freeze". Considering a page with 1000 elements needing laid out, your execution time might easily grow to a minute or more, depending on the complexity of the layout. CSS would handle this natively, and without any "freezing" of your browser. This would cause your page to be unusable for the first bit of time that a person visits, and (according to statistics) you only have 10 seconds to capture the attention of your viewer before they become disinterested in your page and leave, meaning you drive away all your new visitors.
The only time you should use JavaScript for setting style properties is when you need to change the style at runtime. You should always use CSS for styling where possible because:
CSS tends to be implemented a lot more consistently across browsers than JS
A user may have JS disabled
The "code" to do styling in CSS is a lot terser, and easier to read/write than the equivalent JS code