To display an item (whose key is "myinfo"), previously stored locally in the browser, I use something like:
$('div:first').html( localStorage.getItem('myinfo') );
It works well until I open a PDF generated on this page using wkhtmltopdf. In that case, my DIV's content is empty, showing that the localStorage function returned null.
Now that would suggest to me that the webkit engine underneath wkhtmltopdf does not implement localStorage.
Is that the correct reason for this behaviour?
How else can I store and retrieve stuff locally using javascript and wkhtmltopdf?
Now, I've thought through, and can answer the first part of my question:
Is that the correct reason for this behaviour?
No, it isn't.
The reason my approach won't work is:
I saved some data to local storage on "page1.html" in Browser1. Now going to "page2.html" on the same browser, I called wkhtmltopdf (via an AJAX request to the server). Since wkhtmltopdf is essentially another browser (let's call it "Browser2"), there's no way it's going to be able to access data that was previously saved by "Browser1".
Therefore, it's looking increasing to me like: there's no way to programmatically persist data between my Browser1 and wkhtmltopdf without first saving that data on the server. If I am wrong, then my second question:
How else can I store and retrieve stuff locally using javascript and
wkhtmltopdf?
is still waiting for an answer!
Related
I want to save modifications made on a HTML page(modifications made with JQuery), PERMANENTLY! I have read that this thing gets possible by sending an Ajax call and saving it in a table in a database, but what do you actually save in the database? The URL of the page? And what do you retrieve back in the Ajax call so that your modifications actually stay on the page?
This is a Spring MVC based web application, in case this information is needed.
I have no clue how to start or if to start trying saving it, because I have also read that this thing might not be possible, as we're talking about Client-Side modifications.
Modification that I am trying to make:
function versionOne() {
$('#title').addClass('text-center');
$('#title').css({"margin-top":"0px","color":"black", "font-size":"45px"});
$('#title').append('<hr>');
$('#content').addClass('col-md-6');
$('#content').css({"margin-top":"80px","font-size":"20px", "text-align":"center"});
$('#picture').addClass('col-md-6');
$('#picture').css({"border-radius":"25px", "margin-top":"50px"});
}
I'd be grateful for some suggestions!
Thanks :)
Saving the whole page won't work in most cases since it's very hard to also save the JavaScript state. So while you can save a static copy of the page without JavaScript with $('html').html(), that doesn't get you very far (or causes more trouble than it's worth).
What you want is "preferences". The site should remember some specific values. The usual approach is to load the preferences from the database before the server sends the page for the client. Apply them to the elements of the page and send the result to the browser. That way, the page looks as expected when the user sees it.
When the user changes these settings, use JavaScript to update the page and send the changes as AJAX requests to the server to persist them in the database.
When the user returns to the page, the code above will make sure that the page now looks as before.
Is there any way to access the autocomplete suggestions that appear under HTML input fields in some browsers (representing previously submitted data)? Is this only available to the browser?
I ask as I want to make my own autocomplete implementation in javascript, but I want to intermingle my own suggestions with the users previous searches. A bit like how youtube does (but youtube stores all the data obviously, and it is tied to a login, there are no accounts on my website and never will be).
I was wondering more if there was a way to do it with the data stored in the users browser rather than storing all the data on my server. Is there is a way to grab the data the browser uses to present previous input to a user?
Is the data that appears in html input fields representing previously submitted data only available to the browser?
Yes - until it appears in the DOM.
Is there is a way to grab the data the browser uses to present previous input to a user?
It's a browser-specific feature, and you can't access the data [history] directly (Where do browsers save/store auto fill data). You only can disable storing anything.
I ask as I want to make my own autocomplete implementation in javascript, but I want to intermingle my own suggestions with the users previous searches. I was wondering more if there was a way to do it with the data stored in the users browser rather than storing all the data on my server.
Especially if you want to utilize all previous searches, the browser's autofill doesn't help you anyway. But yes, you can store them in the browser (on the client side) manually: Use DOM Storage, like localStorage. Though I would recommend sessionStorage only, you might run into privacy issues otherwise if everybody using a browser could see the search terms of previous users…
You can use jstorage. Jstorage lets you store up to 5Mb of data on the client side.
<script src="//cdnjs.cloudflare.com/ajax/libs/json2/20110223/json2.js"></script>
<script src="https://raw.github.com/andris9/jStorage/master/jstorage.js"></script>
<script>
/* $.jStorage is now available */
// store some data
$.jStorage.set('yourkey', 'whatever value');
// get the data back
value = $.jStorage.get('yourkey');
</script>
The only way i see this working is with help of localStorage (html5) problem that it doesn't work in ie<8
Here's an example: http://jsfiddle.net/8NZY7/
I'm using a JSON file to autopopulate a drop down list. It's by no means massive (3000 lines and growing) but the time taken to refresh the page is becoming very noticeable.
The first time the page is loaded the JSON is read, depending on what option the user has selected dictates which part of the JSON is used to populate the drop down.
It's then loaded on every refresh or menu selection after. Is it possible to somehow cache the values to prevent the need for it to be reloaded time and time again?
Thanks.
EDIT: More Info:
It's essentially a unit converter. The JSON holds all the details. When a users selects 'Temp' for example a call is made and the lists are populated. Once a conversion is complete you can spend all day running temp conversions and they'll be fine but everytime a user changes conversion type so now length, the page refreshes and takes a noticeable amount of time.
Unfortunately, I don't know of a standardized global caching mechanism in PHP. This article says that Optimizer Plus, a third party accelerator, is being included in core PHP starting in version 5.5. Not sure what version you are using but you could try that.
On a different note, have you considered file storage as andrew pointed out? I think it combined with $_SESSION could really help you in this case. Let me give you an example that would work with your existing JSON data:
Server Side
Store your JSON data in a .json file on your PHP server:
{
"data": "some data",
"data2": "more data",
"data3": [
...
],
etc.
}
Note: Make sure to properly format your JSON data. Remember all strings must be enclosed in double quotes ".
In PHP, use an if statement to decide the appropriate action:
error_reporting(E_ALL);
ini_set("display_errors", "On");
session_start();
if(isset($_SESSION['dataCache'])) {
echo json_encode($_SESSION['dataCache']);
} else {
$file = 'data.json';
if (!is_file($file) || !is_readable($file)) {
die("File not accessible.");
}
$contents = file_get_contents($file);
$_SESSION['dataCache'] = json_decode($contents, true);
echo $contents;
}
So lets dig into the above coding a little more. So here's what we are doing in a nutshell:
Turn on error reporting and start session support.
Check to see if we've already read the file for this user.
If so, pull the value from storage and echo it out and exit. If not continue below.
Save off the file name and do a little error checking to ensure PHP can find, open and read the contents of the file.
Read the file contents.
Save the decoded json, which is not an array because of the `true` parameter passed to `json_decode`, into your `$_SESSION` variable.
Echo the contents to the screen.
This will save you the time and hazzle of parsing out JSON data and/or building it manually on the server. It will be cached for the users session so that they can use it through out.
Client Side
I assume you are using ajax to fetch the information? If not correct me, but I was assuming that's where some of your JavaScript comes into play. If so you may consider this:
Store the returned data in sessionStorage on the user's browser when it's returned from the server:
$.ajax({
...
success: function (res) {
localStorage.setItem("dataCache", JSON.stringify(res));
},
...
});
Or if you use promise objects:
$.ajax({
...
}).done(function (res) {
localStorage.setItem("dataCache", JSON.stringify(res));
});
When you need to read it you can do a simple test:
var data;
// This returns null if the item is not in local storage.
// Since JavaScript is truthy falsy, it will be evaluated as false.
if(localStorage.getItem("dataCache")) {
data = JSON.parse(localStorage.getItem("dataCache"));
} else {
// Make ajax call, fetch object and store in localStorage in the success or done callbacks as described above
}
Notes:
localStorage is a new feature in HTML5, so it's not fully supported on all browsers yet. Most of the major ones do however, even as far back as IE8 (I think). However, there is no standardized size limit on how much these browsers are required to hold per site.
It's important to take that into consideration. I can guarantee you probably will not be able to store the entire 30,000 line string in localStorage. However, you could use this as a start. Combined with the server side solution, you should see a performance increase.
Hope this helps.
I use the browser's cache to ensure that my large chunk of JSON is only downloaded once per session. I program in ASP.NET, but I'm sure PHP has the same mechanisms:
On session start, I generate a random string as session key for my dynamic JavaScripts. This key get stored in the ASP.NET session state under the key JsonSessionID. That way I can refer to it in my page markup.
I have a "generic http handler" (an ashx file) that when called by the browser, returns a .js file containing my JSON.
In my HTML I include the dynamic script:
<script type="text/javascript" src="/dynamicJSON.ashx?v=<%= JsonSessionID %>"></script>
The browser will automatically cache any URLs included as scripts. The next time the browser is asked to load a cached script from a URL, it will just load up the file from the local disk. This includes dynamic pages like this.
By adding the ?v= in there, I ensure that the JSON is updated once per session.
Edit
I just realized that your JSON is probably static. If that's the case, you can just put your JSON into a static .js file that you include in your HTML, and the browser will cache it.
// conversionData.js
var conversionData = { "a":1,"b":2,"c":3 };
When you include the conversionData.js, the conversionData variable will be in scope with the rest of your page's JavaScript that dynamically updates the drop-downs.
Edit 2
If you are serving static files, this blog post has a good pattern for cache-busting based on the file's date modified property. i.e. the file is only downloaded when it is changed on the server.
I have yet to find a good method for cache-busting JSON created via database lookup tables, other than per-session. Which isn't ideal because the database could change mid-session.
Once you've got your JSON data decoded into an object you can just keep the object around, it should persist until a page reload at least.
If you want to persist between reloads you might want to look at HTML5's localStorage etc.
You would need to come up with an age strategy, maybe just dump the current date in there with it as well so you can compare that and expire as needed.
I would suggest storing your json data to a session. On first page load you can write a script to get your json data, then store them into a session.
on each page load/refresh afterwards you can check our session to decide what to do - use the session data or fetch again your json data.
This approach suites me for small scale data (for example: an array of products - colors - sizes - prices).
Based on your data you should test you loading times.
Here is a simple hack:
Create a call to a php file as GET request with parameter "bla-bla.html"
or "bla-bla.css"... well you know, it makes browser think it is not a php, but rather "html" or "css". And browser will cache it.
To verify that the trick is working - go to the "network" tab of the browser dev panel and you will see column "type" there along with "transferred" - instead of having php there and actual size, you will find "html" and "(cached)"
This is also good to know when you passing parameters like "blah-blak.html" to the php file and expect it will not be cached. Well, it will be cached.
Tested on FireFox Quantum 57.0.1 (Mac 64bit)
P.S.
Chrome 63 on Mac is capable of recognising real file type in this situation. So it cannot be fooled.
Thinking out of the box here:
but if your list has 3000 lines and growing (as you said)
is it possible for you to establish its maximum size ?
let's say the answer is 10,000 (max) items; then do you really need an ajax call ?
you could transfer the data straight away with the page
(depending on your architecture of course, you could come out with different solution)
I have the following situation: the user submits a form, I fetch the data from the server via an Ajax request and displays a chart. However, I want to give the user the option to display the data in the chart in table form or export as csv after he had submitted the form.
I was wondering what's the best solution to store the data, considering that I don't want the data to persist if the user opens a new window to submit the form again for example.
The application is in Rails.
Thanks.
You have a few options:
Cookies
LocalStorage
SessionStorage
More info: https://developer.mozilla.org/en/DOM/Storage
Non-standard:
window.name can store anywhere from 1mb up to 10mb depending on the browser. This is more of a hack, but is fairly stable. You would need to implement your own accessor/setter methods on this, where localStorage and sessionStorage have API's built in.
Personally i would recommend local storage if all your users browsers support it.
Its very simple to use and you can access it using these to methods.
localStorage.getItem("Itemkey");
localStorage.setItem("Itemkey","value");
localStorage.removeItem("ItemKey");
Its always a good way to go and this means you can assign each window a differnt local storage key and even remove the item when the window is closed, or unloaded !
For reference I found this very useful: http://diveintohtml5.info/storage.html
And combine it with storing JSON objects ( http://www.json.org/js.html ) and you have a very fast,simple and easy to use solution. OR even just store a string,array or what ever is required.
I am developing a flex component in Flex3 which needs to store some data on the local disk for the future use using
var localData:Sharedobject=SharedObject.getLocal("localdata");
Today while i was working on this, eventually i had opened my chrome browser in incognito mode, so the data was not stored and i couldn't restore the data which i has saved earlier.
So i want to know is there any way to check if the local storage is allowed or not; using javascript. Javascript because i want to check it before even my component is loaded. Pls suggest me some ways to do it.
SharedObject.getLocal() throws an Error when it fails to create SO, so just listen for this error.
EDIT
If you need javascript solution you can create a simple Flash/Flex file which will try to create a SharedObject, then it can pass the result (true/false) to Javascript (using ExternalInterface).
Then you can pass the result to your main component...
JS can't access flash SharedObjects.
*EDIT 2 *
There is HTML5 localStorage, so you may want to use that one, but from your question I understood you wanted to check if Flash local storage works.