I just recently started learning javascript and have a question regarding the'proper use'. I'm still trying to identify the role of Javascript within a website, and I'm curious whether or not it would be considered ok to have Javascript modified the HTML of a web page.
Let's say I have a panel on a web page. This panel houses a list. I would like users to be prompted to add items to this list.
I was thinking that it would be possible to use Javascript to generate list items to add to the list. However, this would be modifying the actual number of HTML elements on the web page... For some reason, this just seems 'hacky'. When I think of HTML, I think of a static structure that should come to life with CSS and Javascript.
So my question: is it considered okay to have Javascript modify the HTML of a web page? What about the case of adding items to a list?
Thank you!
Javascript is a programming language designed so it can modify the document that is being displayed(the DOM), the actual HTML is never touched.
Javascript has a place on a website and modifying the document/dom is perfectly acceptable and without it, would make javascript almost useless. CSS is great for certain tasks, but you can't do everything in CSS, though CSS5 is coming pretty close for many tasks.
Rewriting the entire DOM IS bad practice, but using it to shift an element's position based on an action, or creating a popup overlay is perfectly acceptable.
Remember the gold rule:
Modify as little as possible to accomplish the goal.
What matters is the user's experience of the (HTML) document. The representation of "the document" can change by utilising a language like javascript that "manipulates the DOM" - and the DOM is like an instance of the HTML document, or "document session" if you will.
So in a way, no, the HTML is touched. It is positively manhandled by javascript - indirectly and in a non-persistent way. But if you want to be pedantic... we say it isn't and leave half the readers confused.
When to use javascript and when not to. It's swings and roundabouts. You need to learn (mostly from experience) when one particular tool suits the situation. It usually boils down to some core considerations:
HTML is for markup. Structure. Meaning.
CSS is for style, feel, appearance.
Javascript is for those situations where none of the above work.
And I'm neglecting to mention server-side processing with the obvious disclaimer that all processing that ought to be done in privacy is done on the server (with a programming language like PHP or Ruby for example).
Sometimes you get the grey area in-between where you can do something either way. Those situations you may ask yourself a question like... would it be processed quicker if the client (user's computer) processes it, or the server... and that's where experience comes in.
It depends on the case to decide if you should manipulate DOM directly or let the JS do it.
If you have a static html page, just do your html and hand craft the
DOM. There is no need for JS to get a hand here.
If you have a semi static html page where the user actions change
part of it - then get the JS to do the changing part.
If you have a highly dynamic html page (like single page app) - you
should get the JS to render html mostly.
Using plain JS however is not the best for you in this age of great JS evolution. Learn it -but also learn to use good libraries and frameworks which can take you to the track very fast.
I recommend you to learn Jquery and Angular 2 which make you feel like learning a super set of JS straightaway.
Short disclamer: Javascript may modify DOM content in a browser but never change original HTML served from Web server.
Modern Web is unthinkable without javascript. JS allows to make static HTML interactive and improve User Experience (UX). As any sharp tool JS can produce a masterpiece out of nearly dead page and cut throat to a blooming static content.
Everything is up to the developer.
When not to use JS
Do not use JS to deliver ever-green content to the page. Web bots (crawlers) don't run JS, and you message "I come to this world to testify to the truth" may appear "a voice of crying out of desert" and be non-indexed and thus unread.
When JS in the must
Every time your page visitor does something the page should respond with proper action (using JS or, if possible, just CSS).
This is especially important when a prospect fills in a form. To err is human so a developer via JS should help the visitor to make wrong things right. In many cases it is possible without requesting server and in even more cases the answer should come from the server. And JS is your best friend in this case.
Javascript never lives alone. Browser object is its trustful ally. Most modern browsers support XMLHttpObject A.K.A AJAX (you may remember this name from ancient Greek history) which communicates with the server without reloading the page.
The idea of AJAX which stands for Asynchronous Javascript And Xml is to send request and receive response from the server asynchronously without blocking page in the browser.
Native javascript may be difficult to understand to many beginner developers. To make thing easier there are a lot of JS libraries with jQuery being most known.
Returning to the OP's question, Should Javascript be used to modify HTML?
The answer is: It Depends.
Related
Ok so im learning javascript and I just wanted to know if its possible to make it do actions on external pages. For example if I wanted to say 'onload redirect to somesite.com/page1 then once on somesite.com/page1 fill in register form with these details'
is that possible?
You cannot do this.
This would represent, for lack of a better word, an enormous security hole.
The only way to make an external page "do stuff" is to write code that is on or explicitly included in that page itself. Period.
I have however, seen external pages get loaded INTO the current page as strings, and then have the javascript that loaded those pages modify that markup directly. But that is ugly.
On the first page you could modify some variables/values in a database. Then, in the second page you could check the values in your database, and do different "stuff" depending on those values.
You would need to set up a database and use some server-side scripting along with Javascript (server-side scripting is used to interact with your server/database). In your first page, the server-side script, like PHP, would fetch info from your Javascript. In your second page, your Javascript would fetch info from your server side script and then do stuff to that page.
This is a much safer way. If you are taking user input from things like HTML fields, you need to look into cleaning the input to prevent something called "cross-site scripting (XSS)".
You could do this IF you were rendering the other page in a frame of some sort.
There are multiple ways in which you can render an entire external page as a piece of your page. Many pages take precautions to block being rendered in a frame for just this very reason though (Not to mention copyright issues).
Once you're rendering the external page inside your page you should be able to reference components nested in your frame and do the sort of thing that you're describing.
There's no way to do this with JavaScript. The developers of all the major browsers work very, very hard to prevent this sort of thing. If this were possible, it would open up pretty massive security holes.
If you really want to use something like this for testing, you can look at browser automation software like Selenium. This allows you to automate various testing scenarios in your browser, but it does not affect other clients using your site.
Recently, I have come up with some idea about how to improve the overall performance for
a web application in that instead of generating a ready-to-show html page from the web server, why not let it be fully generated in the client side.
Doing it this way, only pure data (in my case is data in JSON format) needs to be sent to the browser.
This will offload the work of html generation from the server to the client's browser and
reduce the size of the response packet sent back to users.
After some research, I have found that this framework (http://beebole-apps.com/pure/)
does the same thing as mine.
What I want to know is the pros and cons of doing it this way.
It is surely faster and better for web servers and with modern browser, Javascript code can run fast so page generation can be done fast.
What should be a downside for this method is probably for SEO.
I am not sure if search engines like Google will appropriately index my website.
Could you tell me what the downside for this method is?
Ps: I also attached sample code to help describe the method as follows:
In the head, simple javascript code will be written like this:
<script type='javascript' src='html_generator.js'/>
<script>
function onPageLoad(){
htmlGenerate($('#data').val());
}
</script>
In the body, only one element exist, used merely as a data container as follows:
<input type='hidden' id='data' value='{"a": 1, "b": 2, "c": 3}'/>
When the browser renders the file, htmlGenerate function which is in html_generator.js will be called and the whole html page will be generated in this function. Note that the html_generator.js file can be large since it contains a lot of html templates but since it can be cached in the browser, it will be downloaded once and only once.
Downsides
Search Engines will not be able to index your page. If they do, you're very lucky.
Users with JavaScript disabled, or on mobile devices, will very likely not be able to use it.
The speed advantages might turn out to be minimal, especially if the user's using a slow JavaScript engine like in IE.
Maintainability: Unless you automate the generation of your javascript, it's going to be a nightmare!
All in all
This method is not recommended if you're doing it only for speed increase. However, it is often done in web applications, where users stay on the same page, but then you would probably be better off using one of the existing frameworks for this, such as backbone.js, and make sure it remains crawlable by following Google's hashbang guidelines or HTML5 PushState (as suggested by #rohk).
If it's just performance you're looking for, and your app doesn't strictly need to work like this, don't do it. But if you do go this way, then make sure you do it in the standardized way so that it remains fast and indexable.
Client-side templating is often used in Single Page Applications.
You have to weight the pros and cons:
Pros :
More responsive interface
Load reduced on your web server
Cons :
SEO will be harder than for a classic website (unless you use HTML5 PushState)
Accessibility : you are relying heavily on javascript...
If you are going this way I recommend that you look at Backbone.js.
You can find tutorials and examples here : http://www.quora.com/What-are-some-good-resources-for-Backbone-js
Examples of SPA :
Document Cloud
Grooveshark
Gmail
Also look at this answer : https://stackoverflow.com/a/8372246/467003
Yikes.
jQuery templates are closer to what you are thinking. Sanity says you should have some HTML templates that you can easily modify at will. You want MAINTAINABILITY not string concatenations that keep you tossing and turning in your worst nightmares.
You can continue with this madness but you will end up learning the hard way. I employ you to first try some protypes using jQuery templates and your pure code way. Sanity will surely overcome you my friend and I say that coming from trying your way for a time. :)
Its possible to load content in dynamically of the template you need as well using AJAX. It doesn't make sense that you will have a panacea approach where every single conceivable template is needed to be downloaded in a single request.
The pros? I really can't think of any. You say that it will be easier in the webserver, but serving HTML is what web servers are designed to do.
The cons? It goes against just about every best practise when it comes to building websites:
search engines will not be able to index your site well, if at all
reduced maintainability
no matter how fast JS engines are, the DOM is slow, and will never be as fast as building HTML on the server
one JS error and your entire site doesn't render. Oops. Browsers however are extremely tolerant of HTML errors.
Ultimately HTML is a great tool for displaying content. JavaScript is a great way of adding interaction. Mixing them up like you suggest is just nuts and will only cause problems.
Cons
SEO
Excluding user without javascript
Pros
Faster workflow / Fluider interface
Small load reduce
If SEO is not important for you and most of your user have Javascript you could create a Single Page Applications. It will not reduce your load very much but it can create a faster workflow on the page.
Btw: I would not pack all templates in one file. It would be too big for big projects.
how good is it to load/render repeating elements in a html page via JavaScript. I know a few(5%) of ppl dont have js enabled. So is it really worth it. I can get up to 15-20% reduction in markup and in turn page size by doing so
If you care about page size, then turn on compression on your server instead.
Repeating content compresses very well, so your 15-20% is going to be a much smaller proportion of the page weight (and the HTML is probably going to be insignificant compared to any images you have anyway).
Avoid content generation with JS if you can, it is another point of failure.
I dont think that 15% reduction in size warrants a run of JS because the JS engines are
really different across all platforms and the extra JS code which works on all Browsers will be of same length.
Moreover the time taken by Browser to compile JS and the make DOM tree and then Add it to the Document and render it will make ur page slow.
IMO you should use js to generate dynamic html. And if user has disabled js then you can give him a warning that "You should enable JavaScript for my website to work best."
If you're not loading the HTML data asynchronously, you could use a server-side language (like PHP) to print the repeating HTML before the page is served to the browser. If that's not an option, then you'll need to either stick with the Javascript you already have or suck it up and type it out manually.
In this day and age, it's mostly acceptable to tell users that they have to have Javascript enabled to view your website.
In my opinion, most of the people who have JS disabled on their browser for various reasons (official, security), won't fit the profile of a client for most websites. The reason is that almost all of us are targeting the regular Joe who is uses Gmail with Ajax, and experiences the web in multimedia.
I would recommend using JS if it is making your product work better.
When a developing a web app, versus a web site, what reasons are there to use multiple HTML pages, rather than using one html page and doing everything through Javascript?
I would expect that it depends on the application -- maybe -- but would appreciate any thoughts on the subject.
Thanks in advance.
EDIT:
Based on the responses here, and some of my own research, if you wanted to do a single-page, fully JS-Powered site, some useful tools would seem to include:
JQuery Plug Ins:
JQuery History:
http://balupton.com/projects/jquery-history
JQuery Address:
http://plugins.jquery.com/project/jquery-address
JQuery Pagination:
http://plugins.jquery.com/project/pagination
Frameworks:
Sproutcore
http://www.sproutcore.com/
Cappucino
http://cappuccino.org/
Possibly, JMVC:
http://www.javascriptmvc.com/
page based applications provide:
ability to work on any browser or device
simpler programming model
they also provide the following (although these are solvable by many js frameworks):
bookmarkability
browser history
refresh or F5 to repeat action
indexability (in case the application is public and open)
One of the bigger reasons is going to be how searchable your website is.
Doing everything in javascript is going to make it complicated for search engines to crawl all content of your website, and thus not fully indexing it. There are ways around this (with Google's recent AJAX SEO guidelines) but I'm not sure if all search engines support this yet. On top of that, it's a little bit more complex then just making separate pages.
The bigger issue, whether you decide to build multiple HTML pages, or you decide to use some sort of framework or CMS to generate them for you, is that the different sections of your website have URL's that are unique to them. E.g., an about section would have a URL like mywebsite.com/about, and that URL is used on the actual "about" link within the website.
One of the biggest downfalls of single-page, Ajax-ified websites is complexity. What might otherwise be spread across several pages suddenly finds its way into one huge, master page. Also, it can be difficult to coordinate the state of the page (for example, tracking if you are in Edit mode, or Preview mode, etc.) and adjusting the interface to match.
Also, one master page that is heavy on JS can be a performance drag if it has to load multiple, big JS files.
At the OP's request, I'm going to discuss my experience with JS-only sites. I've written four relevant sites: two JS-heavy (Slide and SpeedDate) and two JS-only (Yazooli and GameCrush). Keep in mind that I'm a JS-only-site bigot, so you're basically reading John Hinkley on the subject of Jody Foster.
The idea really works. It produces gracefully, responsive sites at very low operational costs. My estimate is that the cost for bandwidth, CPU, and such goes to 10% of the cost of running a similar page-based site.
You need fewer but better (or at least, better-trained) programmers. JavaScript is an powerful and elegant language, but it has huge problems that a more rigid and unimaginative language like Java doesn't have. If you have a whole bunch of basically mediocre guys working for you, consider JSP or Ruby instead of JS-only. If you are required to use PHP, just shoot yourself.
You have to keep basic session state in the anchor tag. Users simply expect that the URL represents the state of the site: reload, bookmark, back, forward. jQuery's Address plug-in will do a lot of the work for you.
If SEO is an issue for you, investigate Google Ajax Crawling. Basically, you make a very simple parallel site, just for search engines.
When would I not use JS-only? If I were producing a site that was almost entirely content, where the user did nothing but navigate from one place to another, never interacting with the site in a complicated manner. So, Wikipedia and ... well, that's about it. A big reference site, with a lot of data for the user to read.
modularization.
multiple files allows you to mre cleanly break out different workflow paths and process parts.
chances are your Business Rules are something that do not usually directly impact your layout rules and multiple files would better help in editing on what needs to be edited without the risk of breaking something unrelated.
I actually just developed my first application using only one page.
..it got messy
My idea was to create an application that mimicked the desktop environment as much as possible. In particular I wanted a detailed view of some app data to be in a popup window that would maintain it's state regardless of the section of the application they were in.
Thus my frankenstein was born.
What ended up happening due to budget/time constraints was the code got out of hand. The various sections of my JavaScript source got muddled together. Maintaining the proper state of various views I had proved to be... difficult.
With proper planning and technique I think the 'one-page' approach is a very easy way to open up some very interesting possibilities (ex: widgets that maintain state across application sections). But it also opens up many... many potential problem areas. including...
Flooding the global namespace (if you don't already have your own... make one)
Code organization can easily get... out of hand
Context - It's very easy to
I'm sure there are more...
In short, I would urge you to stay away from relying on JavaScript dependency for the compatibility issue's alone. What I've come to realize is there is simply no need rely on JavaScript to everything.
I'm actually in the process of removing JavaScript dependencies in loo of Progressive Enhancement. It just makes more sense. You can achieve the same or similar effects with properly coded JavaScript.
The idea is too...
Develop out well-formatted, fully functional application w/o any JavaScript
Style it
Wrap the whole thing with JavaScript
Using Progressive Enhancement one can develop an application that delivers the best possible experience for the user that is possible.
For some additional arguments, check out The Single Page Interface Manifesto and some (mostly) negative reaction to it on Hacker News (link at the bottom of the SPI page):
The Single Page Interface Manifesto: http://itsnat.sourceforge.net/php/spim/spi_manifesto_en.php
stofac, first of all, thanks for the link to the Single Page Interface (SPI) Manifesto (I'm the author of this boring text)
Said this, SPI != doing everything through Javascript
Take a look to this example (server-centric):
http://www.innowhere.com/insites/
The same in GAE:
http://itsnatsites.appspot.com/
More info about the GAE approach:
http://www.theserverside.com/news/thread.tss?thread_id=60270
In my opinion coding a complex SPI application/web site fully on JavaScript is very very complex and problematic, the best approach in my opinion is "hybrid programming" for SPI, a mix of server-centric for big state management and client-centric (a.k.a JavaScript by hand) for special effects.
Doing everything on a single page using ajax everywhere would break the browser's history/back button functionality and be annoying to the user.
I utterly despise JS-only sites where it is not needed. That extra condition makes all the difference. By way of example consider the oft quoted Google Docs, in this case it not only helps improve experiences it is essential. But some parts of Google Help have been JS-only and yet it adds nothing to the experience, it is only showing static content.
Here are reasons for my upset:
Like many, I am a user of NoScript and love it. Pages load faster, I feel safer and the more distracting adverts are avoided. The last point may seem like a bad thing for webmasters but I don't want anyone to get rewarded for pushing annoying flashy things in my face, if tactless advertisers go out of business I consider it natural selection.
Obviously this means some visitors to your site are either going to be turned away or feel hassled by the need to provide a temporary exclusion. This reduces your audience.
You are duplicating effort. The browser already has a perfectly good history function and you shouldn't need to reinvent the wheel by redrawing the previous page when a back button is clicked. To make matters worse going back a page shouldn't require re-rendering. I guess I am a student of If-it-ain't-broke-don't-fix-it School (from Don't-Repeat-Yourself U.).
There are no HTTP headers when traversing "pages" in JS. This means no cache controls, no expiries, content cannot be adjusted for requested language nor location, no meaningful "page not found" nor "unavailable" responses. You could write error handling routines within your uber-page that respond to failed AJAX fetches but that is more complexity and reinvention, it is redundant.
No caching is a big deal for me, without it proxies cannot work efficiently and caching has the greatest of all load reducing effects. Again, you could mimic some caching in your JS app but that is yet more complexity and redundancy, higher memory usage and poorer user experience overall.
Initial load times are greater. By loading so much Javascript on the first visit you are causing a longer delay.
More JavaScript complexity means more debugging in various browsers. Server-side processing means debugging only once.
Unfuddle (a bug-tracker) left a bad taste. One of my most unpleasant web experiences was being forced to use this service by an employer. On the surface it seems well suited; the JS-heavy section is private so doesn't need to worry about search engines, only repeat visitors will be using it so have time to turn off protections and shouldn't mind the initial JS library load.
But it's use of JS is pointless, most content is static. "Pages" were still being fetched (via AJAX) so the delay is the same. With the benefit of AJAX it should be polling in the background to check for changes but I wouldn't get notified when the visible page had been modified. Sections had different styles so there was an awkward re-rendering when traversing those, loading external stylesheets by Javascript is Bad Practice™. Ease of use was sacrificed for whizz-bang "look at our Web 2.0" features. Such a business-orientated application should concentrate on speed of retrieval, but it ended up slower.
Eventually I had to refuse to use it as it was disrupting the team's work flow. This is not good for client-vendor relationships.
Dynamic pages are harder to save for offline use. Some mobile users like to download in advance and turn off their connection to save power and data usage.
Dynamic pages are harder for screen readers to parse. While the number of blind users are probably less than those with NoScript or a mobile connection it is inexcusable to ignore accessibility - and in some countries even illegal, see the "Disability Discrimination Act" (1999) and "Equality Act" (2010).
As mentioned in other answers the "Progressive Enhancement", née "Unobtrusive Javascript", is the better approach. When I am required to make a JS-only site (remember, I don't object to it on principle and there are times when it is valid) I look forward to implementing the aforementioned AJAX crawling and hope it becomes more standardised in future.
I'm creating a blog, but I need box-shadows for my boxes, so I'm asking the following.
Is it good to add shadows via a)images/css or b)javascript?
I've heard that lot of people don't have javascript enabled while browsing, so is there this a problem? It would be easier and simpler to create these shadows with javascript than adding a million divs and positioning them.
EDIT: I found this page: http://www.w3schools.com/browsers/browsers_stats.asp and it says that almoset every user has js enabled.
You could use JavaScript for your layout, but the general principal that you should keep in mind is that your HTML should be semantic: the elements on the page should have a meaning; it should project a structure that goes beyond the design of the page (although that structure can certainly be used as an indcator for the design aspects as well).
When this principal is applied, using JavaScript can help with providing the style you wish to project given the semantic meaning of the page.
Also, you should check your server logs (your hosting provider should have some sort of analytics tool/report available) which should tell you what browsers and versions are being used to visit your site. With that information, you can get a good feel for the people that you are currently reaching.
If you are using some sort of analytics package (e.g. Google Analytics) then you can possibly see the delta between two periods of time for the new visitors to your site as well, and try to gauge the capability of the browsers that new users will be using when they visit your site.
A few things to consider when using JavaScript to manipulate the DOM on the front end:
If you are using JavaScript to manipulate a good deal of the content, it's going to be a client-side process, and that can slow down the rendering of your page. You might want to consider a theme/template for your blog/cms which gives you the styling that you want and is rendered through CSS on the server-side.
Search engines do not execute your JavaScript. Because of this, you want to avoid manipulating the indexable content at all costs. You want your content to be embedded in the HTML as it is sent from the server. Using AJAX or other JavaScript to manipulate certain things is fine, but when it comes to your content, unless you are stylizing it, do not use JavaScript to manipulate it
Use CSS box-shadow for nice, up-to-date browsers: http://css-tricks.com/snippets/css/css-box-shadow/ (requires no extra markup)
And for most everyone else, serve up your js solution.
You should do it the easiest way for you and allow the page to degrade gracefully for those without JS (If you think you need to consider them, as today, I don't see any point in building none JS sites or building sites for no-js users).