I'm creating a website, that has a button, I want it to work in such way that whenever someone clicks it a number is increased by one, I want this number not to be reset when the page is refreshed or accessed from somewhere else.
Please help me with a sample code... Im a beginner
As mentioned by #SLaks, you will need some method of storing this counter on the server - otherwise there is no way for a page request to know how many times it has been called before. To do this you will need both:
Server-side code to read the value and display it to the user, and also to update the value when the page is requested the next time, and
Server-side storage to actually hold the counter value.
One possible solution to this (without adding a huge amount of additional complexity) would be to use PHP to read/write the counter, and a simple text file to hold the value. There are other ways, but may make things a bit too hard (i.e. no need for a database to hold one value).
Related
We have a page which contains a lot of user editable data that is populated from various tables in a database. The data is in all different forms, dropdowns, checkboxes, input boxes, text areas, etc...
There have been some conflicts where two users load a record around the same time, one makes changes, and then another makes a set of changes. When they save they are unaware someone else made a change and may have just broken a change they made or overwrote their change.
I am trying to implement a solution to mitigate this problem, such as flashing the user an error when the data was changed by someone else.
I am wondering if there is a best practice way to check for this problem? Some ideas I had are
Submit both 'current' data present in the field, and the 'original' data. Then check which are changed and compare them in the database to see if the defaults differ from what is currently saved. This would work, but seems to be the least performance friendly.
Use jquery/javascript to detect when a field has been edited, and if it has changed from defaultValue then set a hidden field which will be submitted to indicate it's original value. Then it would do similar to what the previous idea did.
Set a hidden field with a timestamp of when the user loaded their page. When they submit, use that timestamp and check our history table to see if any data on the page was changed since that timestamp. This seems to be the most efficient idea and likely easiest to implement.
Are there any better options or a best practice way to do this? I feel like I am reinventing the wheel for a common problem.
You are solving a common problem. But it's common because it needs repeatedly solved so frequently. "Optimistic Record Locking" is your path forward. It looks like yii (which I am not familiar with) has capabilities to incorporate handling this. I found this link.
Whether the yii infrastructure does this for you, or you have to build it yourself, what you want to do (to support Optimistic Record Locking) is the following:
Make and Keep an unchanged copy of your data when you retrieve it to the Client.
The Client must submit the changes together with the unchanged copy of the data back to the server.
The Server's 'update' routine compares the unchanged
copy to the current record(s). If something has been changed, then it must
return an error msg and the 'new' current record.
If nothing was changed, then the Server does the update.
The alternative is Pessimistic Record Locking, which you can check out. I avoid it due to other issues it has, but there are scenarios where it is more appropriate.
Coming from Python/Java/PHP, I'm now building a website. On it I want a list of items to be updated in near-realtime: if items (server side) get added to or deleted from the list, this should be updated on the webpage. I made a simple API call which I now poll every second to update the list using jQuery. Because I need some more lists to be kept updated on the same page I'm afraid this will turn into more than 10 server calls per second from every single open browser, even if nothing gets updated.
This seems not like the logical way to do it, but I don't really know how else to do it. I looked at Meteor, but since the webpage I'm building is part of a bigger system I'm rather restricted in my choices of technology (basic LAMP setup).
Could anybody enlighten me with a tip from the world of real-time websites on how to efficiently keep a list updated?
You can use WebSocket(https://code.google.com/p/phpwebsocket/ ) technology.
but php is not the best language for implement it
A way to work this is using state variables for the different types of data you want to have updated (or not).
In order to avoid re-querying the full tables even if the data set in them has not changed in relation to what a particular client has displayed at any given time, you could maintain a state counter variable for the data type on the server (for example in a dedicated small table) and on the client in a javascript variable.
Whenever an update is done on the data tables on the server, you update the state counter there.
Your AJAX polling calls would then query this state counter, compare it to the corresponding javascript variable, and only do a data-update call if it has changed, updating the local javascript variable to what the server has.
In order to avoid having to poll for each datatype separately, you might want to use an JS object with a member for each datatype.
Note: yes this is all very theoretical, but, hey, so is the question ;)
I am using the below javascript to load the captcha in my site. This is working fine.But in my first login it defaultly show the number "5AbD". How can i change it.
http://wiki.asp.net/page.aspx/1369/simple-captcha-code-in-javascript/
I user the above link javascrtipt. I can't able to post this script here..
You dont provide many details, but often something like this is related to a random number being generated every time with the same seed. If you rolled your own captcha I would look into how you are generating the string. Commonly one passes the system tick count as the random number seed.
Otherwise, you don't really provide enough information for anyone to give a helpful answer.
Edit:
1) After seeing your code, first I want to say that as captcha this is extremely flawed. The whole point is that a bot cant determine the code and automatically enter it. This is why they are usually images generated on the server. It is difficult to extract the value from an image.
2) It is showing the same value every time because you have not coded it otherwise. You are literally starting with the same -hard coded- value and modifying that. Look into the Math.random() function for generating a random number for the initial value instead of hard coding that. But, referencing point #1, I would scrap this whole javascript thing altogether because as captcha it's useless because a bot could just grab the value of that control and fill out the form with it.
3) The steps for implementing captcha are usually something like: generate the random string on the server, save that string to session, generate an image with that string (with some noise/font funkiness to prevent an image processor from easily being able to read the text), then display the image on the page. The actual string value never leaves the server. When the form is submitted, you just compare the user value with the value you previously stored in the session. But rather than go through all of that (unless the whole point is as a learning exercise), you might think about using any of the pre-made captcha controls such as recaptcha, etc. Either way, look into the random number function, because as long as you are always starting with the same hard coded values then you will always get the same result.
I want to write a little game where the users has to click on appearing elements/objects in a given time. In detail the objects appears in holes onto the ground and after x seconds the objects disappear. The gamer has y lifes and all clicks gets counted until he lost the game.
After that his highscore gets posted to a database (via form post or AJAX). Long story short how can I avoid the user faking his highscore before sending? The program language is JS.
I know its not possible to hide all the code and make it not hack-able. But I think it's enough if the code is so difficult that the user has to do a lot of work to understand where he has to intervent to send faked data.
Has anybody some ideas howto make the code as difficult as its possible?
Thanks in advance for any ideas :)
You should never really try to make your source code unreadable. It will make as great a headache for yourself than any obstruction to anyone modifying it.
That said, you could refactor all your variable names to complete gibberish and play with whitespace, but anyone seriously trying to understand your code could revert that in a decent text editor. To make it any more complex would take away from the efficiency of your program - otherwise you could fill it with useless calls to functions that don't do anything and strange incrementation of counters that the program does not depend on.
there are compressors that do exact the job you want! Some of them can be downloaded and used as offline tools, some are directly via web accessible:
http://javascriptcompressor.com
like jquery and others you can use your code to maintain the scripts and deliver a faster loadable packed version that is hardly readable
How about this:
Create two PHP pages, with one containing the game interface and the other containing the game's code. Program the first one so that it creates a one-time-use string that the tag will pass along as a parameter when it calls the JS code from the second one. Program the second one so it checks the validity of the string sent. If the string is valid, the script should output the JS code, then invalidate the string.
Then, when the user copies the URL of the script, pastes it into his browser, and hits "Return," all he sees is either a blank page or a "not authorized" message.
I'm building what I am hoping to be a fairly simple, quick and dirty demo app.
So far, I've managed to build a bunch of components using only html and javascript. I know that eventually I'll hook-up a db, but at this point I'm just trying to show off some functionality.
In the page, a user can select a bunch of other users (like friends). Then they go to a separate html page and there is some sorting info based on the selected users.
So my first attempt was to put the selected users object into a cookie, and retrieve the cookie on the second page. Unfortunately, if the user changed their selection, the cookie wasn't getting updated, and my searches on StackOverflow seemed to say that deleting and updating cookies is unreliable.
I tried
function updateCookie(updatedUserList){
jQuery.cookie('userList',null);
jQuery.cookie('userList',updatedUserList);
}
but though it set the cookie to null, it wouldn't update it on the second value.
So I decided to put the selected users object into a form. Unfortunately, it looks like I can't retrieve the contents from the form on the client-side, only on the server-side.
Is there another way to do this? I've worked in PHP and Rails, but I'm trying to do this quickly and simply before building it out into something larger and am trying to avoid any server-side processing for now, which I have managed to do up to this point.
Since this is a demo, can you use HTML5? If so, you can use local storage: link text.
Another option is to use AJAX to load the other HTML page (replace whole body of the current document). Your storage variables would be stored in the <head>. This is a tightly coupled design, but again you're making a quick and dirty demo.
Is updatedUserList a string? If it's an array you might have to stringify it first:
jQuery.cookie('userList', JSON.stringify(updatedUserList))
(and of course parse it when you're retrieving it.)