I'm getting into using IndexedDB. Thought I'd grab Parashuram's jQuery wrapper for it.
However, there doesn't seem to be a whole lot of information regarding IndexedDB lying around the internet.
Does anyone know what the I/O speeds are like on IndexedDB, preferably browser-specific? Is there any way to measure it? How would using the jQuery wrapper (as well as the polyfill shim to make it work in Opera/Safari) affect these speeds?
Reason I'm asking is I thought to store snippets of HTML content in the base, but maybe I shouldn't bother if fetching it would take longer than browser cache or similar.
It depends on the browser your are using.
My experience is that IE 10 is pretty fast, compared to chrome and FireFox. Try my QUnit test I wrote for my framework, and you will really see the difference. Of course this isn't a benchmark test, only test of functionality.
Related
I am working on a project to convert a web site that is fully functional in Internet Explorer 8 and lower, but does not work well in Firefox or Safari.
A lot of what will need to be changed is going to be javascript-related (aka methods that exist in IE but not in other browsers).
What I want to know is whether anyone is aware of a fairly comprehensive list of common things that have to be changed to work accross all browsers.
I am starting with quirksmode.org but I don't think it will have quite everything I'm looking for. If anyone knows of a list please let me know.
Your best option here is to go with a Javascript toolkit/library like jQuery, MooTools or Prototype. Such a decision will save you a monstrous amount of work, and all three are constantly being updated which gives you a large degree of safety against future compatibility issues. Especially for DOM manipulation or AJAX, a library is the way to go.
If you absolutely mustn't use one, quirksmode is a good start. I've never found any single source that is comprehensive enough to keep me from running back to Google for each problem area.
Quite honestly, if you don't have lots of experience doing cross-browser development, I suspect the best way to fix your app is to set up a good test environment on each target browser and starting finding where it breaks. You're eventually going to have to test it on each target browser anyway, so you might as well start there. Once you find out what code is failing you for a particular bug, you can do more targeted searches for how to work around that issue in a cross browser way.
You will, over time, build up a good internal knowledge base of what is safe to use in a cross browser way and what is not. Even experienced developers still run into new issues on every project that are only found with testing. One advantage of experience though is that you start to learn when to suspect that something might or might not have cross browser issues and either avoid it (find a safer way) or explicitly test it in several browsers before you use it.
I find that http://jsfiddle.net is awesome for creating very efficient self-contained test cases to either proactively try something in other browsers or to troubleshoot something that's been giving you a problem.
As others have said, one huge advantage of the various browser libraries like jQuery or others is that they have solved a lot of these compatibility issues for you and, in general, if they document a function in the library and don't explicitly warn you about cross-browser issues, then they've already done their homework to make it safe for you.
You may also find out that using a javascript framework such as jQuery, ExtJs, Prototype, Mootols, ... would be very beneficial in writing cross browser javascript.
a web site that is fully functional in Internet Explorer 8 and lower,
but does not work well in Firefox or Safari
I would strongly recommend to develop with a browser that meets the standards (e.g. CSS3).
The process should rather be: to develop with FireFox or Chrome - and fix all IE versions later on.
Well, this is my daily bread... and ordinary it's IE b*tch which makes me loose time...
I want to parse a html-page that unfortunately requires JavaScript to show any content. In order to do so I use a small python-script that pulls the html-code of the page, but after that I have to execute the JavaScript in a DOM-context which seems pretty hard.
To make it even harder I want to use it in a server environment that has no X11-server.
Note: I already read about http://code.google.com/p/pywebkitgtk/ but it seems to need a X-server.
You can simulate a browser environment using EnvJS. However, in order to make use of it, you will have to embed some kind of JavaScript runtime (e.g. Rhino) in your program (or spawn one as an external process).
You could try using Xvfb to have a fake frame buffer, so you won't need to run X11 (though it may be a dependency of Xvfb on your system). Most rendering engines don't have a headless mode, so something like Xvfb is necessary to run them. I used this technique successfully using XULRunner to navigate web pages, though not from python.
I'm still trying to figure this out myself, so take my answer with a grain of salt.
So far, I found http://blog.motane.lu/2009/06/18/pywebkitgtk-execute-javascript-from-python/, which describes the use and the quirks of Pywebkitgtk by someone who has similar needs to what we do.
Later, however, the writer of that blogpost discovered that he can't get it to work with Xvbf, so he hunted some more and found a Qt webkit (possibly in Qt itself, if I understand correctly) http://blog.motane.lu/2009/07/07/downloading-a-pages-content-with-python-and-webkit/. Apparently it's a much better solution than PywebkitGTK.
Naturally, I'll be looking into the other solutions offered here--but I wanted to bring up the Qt solution, because to me, it seems the most likely candidate for what I want to do...and if not, then perhaps it will be for someone else, looking for an answer to this question! :-)
I use VNC or Xvfb for this purpose, combined with Firefox. After experimenting with the two, I settled on XTightVNC. We use it to create screenshots on demand for various test purposes. It's nice to use one of these because you're executing it in an actual browser, same as a user would be (though most users probably won't be using the same OS as your server).
The handy thing about using VNC is that you can connect remotely to set up and test the browser when needed.
This might help: http://code.google.com/p/pyv8/
Does anyone know of a small, fast, javascript emulator with DOM layer support? in either C/C++?
The problem:
I need rudimentary support for javascript in a crawler application, and am wondering if there's any other options other than:
a) Integrating WebKit (headless) (slows down crawling tremendously).
b) Integrating SpiderMonkey and writing the DOM layer myself (not looking forward to this option, not sure if its even worth it, speed wise).
Any other options?
Thanks!
Throw in my vote for WebKit (or some other existing code). Why bother reinventing the wheel, especially when the wheel is really fancy, complicated, has spent years in development.
If you really wanted, you could write some code that checks for javascript first, so you only pass off the jobs that need it. Then, write filters for common ad networks and analytics packages to ignore. If it were me though, I'd rather be consistent with how I am crawling.
Also, don't think that you only need rudimentary support, as there are some really funky websites out there that do a ton of DOM altering. If you expect your crawling to be reliable, be prepared to support what browsers support. The easiest way to do that is use the same code that the browsers are using.
Correction: V8 does not support DOM, just JavaScript, so not what you were looking for...
V8:
http://code.google.com/apis/v8/intro.html
I'm developing a web application that uses lots of Javascript and CSS, both of my own creation and through third-party libraries. These include jQuery and Google Maps & Visualization JS APIs.
I've been testing everything in Firefox 3. Things are peachy until it turns out the main target of this webapp is (cue sad trombone) IE7. I'm looking for caveats, advice, libraries, or other references to help make this transition as easy as possible (not that it's actually going to be easy).
I've already tried IE7.js though it hasn't yet shown itself to be the silver bullet I was hoping for. I'm sure that it works as advertised, I think it's just not as all-encompassing as I'd like (example: colors like #4684EE and #DC3912, which are correctly rendered in FF3, are rendered as black in IE7, with or without IE7.js). Are there other libraries out there to help bring IE7 (more) in line with FF3?
A corollary question: what debugger would you recommend for IE7? I'm currently using Firebug Lite, but it runs painfully slowly. Is there anything out there with similar features that I might have missed?
As far as libraries go, jQuery is compatible across all major browsers, so at least you've got that going for you. Without knowing exactly which plugins/modules/libraries you're using, I can't recommend alternatives that are cross-browser compatible.
You could take a look at the Internet Explorer Developer Toolbar. It isn't nearly as good as Firebug, but it's better than nothing.
Get the IETab add-on for Firefox so that you can fire up IE right inside the same tab you test Firefox in. Get the FULL version of Firebug. It will be perfect for you to deal with HTML, CSS, and scripting. HTMLValidator for validating your HTML and CSS. The Web Developer toolbar is a MUST if you don't have it. I can't even go into a fraction of the benefits it has, from images to source viewing to validating scripts it has a lot.
I use a separate stylesheet for IE7. It doesn't have many changes from the original stylesheet, but enough to make viewing in IE7 close to FF. I try not to do ANYTHING for IE6. In fact I encourage the "downfall" of IE6. It's almost ten years old, and full of bugs, and unsupported now!
Unfortunately, Microsoft doesn't really want to be on the same page as the W3C and developers that want web standards so that you don't have deal with what you're going through right now. Regardless of what they SAY, they're still "competing" against the other browsers for control, and it's hurting the developers.
Writing cross browser code is a big topic - you can't really generalize it into "don't float left and padding-left" statements and be done.
Separate stylesheets for ie are messy and not needed IMO.
Generally speaking, firefox fixes broken code in a good bit of cases, so there is a chance that at least some of your stuff looks bad in IE because of open tags that firefox is fixing for you.
Re-slicing a site that's already done might be your easiest way. You should be able to completely redo the CSS from scratch in a few hours tops.
But all this is advice that may not apply - it would be easier to see the code you're talking about.
I'm not a JavaScript wiz, but is it possible to create a single embeddable JavaScript file that makes all browsers standards compliant? Like a collection of all known JavaScript hacks that force each browser to interpret the code properly?
For example, IE6 does not recognize the :hover pseudo-class in CSS for anything except links, but there exists a JavaScript file that finds all references to :hover and applies a hack that forces IE6 to do it right, allowing me to use the hover command as I should.
There is an unbelievable amount of time (and thus money) that every webmaster has to spend on learning all these hacks. Imagine if there was an open source project where all one has to do is add one line to the header embedding the code and then they'd be free to code their site per accepted web standards (XHTML Strict, CSS3).
Plus, this would give an incentive for web browsers to follow the standards or be stuck with a slower browser due to all the JavaScript code being executed.
So, is this possible?
Plus, this would give an incentive for web browsers to follow the standards or be stuck with a slower browser due to all the JavaScript code being executed.
Well... That's kind of the issue. Not every incompatibility can be smoothed out using JS tricks, and others will become too slow to be usable, or retain subtle incompatibilities. A classic example are the many scripts to fake support for translucency in PNG files on IE6: they worked for simple situations, but fell apart or became prohibitively slow for pages that used such images creatively and extensively.
There's no free lunch.
Others have pointed out specific situations where you can use a script to fake features that aren't supported, or a library to abstract away differences. My advice is to approach this problem piecemeal: write your code for a decent browser, restricting yourself as much as possible to the common set of supported functionality for critical features. Then bring in the hacks to patch up the browsers that fail, allowing yourself to drop functionality or degrade gracefully when possible on older / lesser browsers.
Don't expect it to be too easy. If it was that simple, you wouldn't be getting paid for it... ;-)
Check out jQuery it does a good job of standardizing browser javascript
Along those same lines explorercanvas brings support for the HTML5 canvas tag to IE browsers.
You can't get full standards compliance, but you can use a framework that smooths over some of the worst breaches. You can also use something called a reset style sheet.
There's a library for IE to make it act more like a standards-compliant browser: Dean Edwards' IE7.
Like a collection of all known
javascript hacks that force each
browser to interpret the code properly
You have two choices: read browser compatibility tables and learn each exception a browser has and create one yourself, or use avaiable libraries.
If you want a javascript correction abstraction, you can use jQuery.
If you want a css correction abstraction, you can check /IE7/.
I usually don't like to use css corrections made by javascript. It's another complexity to my code, another library that can insert bugs to already bugged browsers. I prefer creating conditional statements to ie6, ie7 and such and create separate stylesheets for each of them. This approach works and doesn't generate a lot of overhead.
EDIT: (I know that we have problems in other browsers, but since IE is the major browser out there and usually we need really strange hacks to make it work, css conditional statements is a good approach IMO).
Actually you can,there are lots of libraries to handle this issue. From the start of the time, javascript compliance issue always was a problem for developers and thanks to innovative ones who developed libraries to get over this problem...
One of them and my favorite is JQuery.
Before JavaScript 1.4 there was no global arguments Array, and it is impossible to implement the arguments array yourself without a highly advanced source filter. This means it is going to be impossible for the language to maintain backwards-compatibility with Netscape 4.0 and Internet Explorer 4.0. So right out I can say that no, you cannot make all browser standards compliant.
Post-netscape, you can implement nearly all of the features in the core of the language in JavaScript itself. For example, I coded all methods of the Array object in 100% JavaScript code.
http://openjsan.org/doc/j/jh/jhuni/StandardLibrary/1.81/index.html
You can see my implementation of Array here if you go to the link and then go down to Array and then "source."
What most of you are probably referring to is implementing the DOM objects yourself, which is much more problematic. Using VML you can implement the Canvas tag across all the modern browsers, however, you will get a buggy/barely-working performance in Internet Explorer because VML is markup which is not a good format for implementing the Canvas tag...
http://code.google.com/p/explorercanvas/
Flash/Silverlight: Using either of these you can implement the Canvas tag and it will work quite well, you can also implement sound. However, if the user doesn't have any browser plugins there is nothing you can do.
http://www.schillmania.com/projects/soundmanager2/
DOM Abstractions: On the issue of the DOM, you can abstract away from the DOM by implementing your own Event object such as in the case of QEvent, or even implementing your own Node object like in the case of YAHOO.util.Element, however, these usually have some subtle changes to the standard API, so people are usually just abstracting away from the standard, and there is hundreds of cases of libraries that abstract away.
http://code.google.com/p/qevent/
This is probably the best answer to your question. It makes browsers as standards-compliant as possible.
http://dean.edwards.name/weblog/2007/03/yet-another/