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Cache - How to use it? (in firebase for a beginner)

I as a beginner struggle a lot to figure out how you can save reads of data which is constantly queried. Does anybody has some good resources to learn about this. Currently I have a list of exercises, which is frequently refreshed, but the reads are much more compared to the writes. I set it up on firestore and always serve it through ejs (template engine) to my modal. Instead of always querying the same data all the time to my template, can I save the results and just serve them? I could also serve it statically, which wouldn't be so dynamic as it's made by hand. But I could then save a lot of reads and just query the newly added (creation Date after I implemented the data static),or?
In my project I am using just plain HTML and plain JavaScript (Cloud Functions with express)
Is there no common practice for this kind of situation? You could also save the data like every hour on Google cloud platform as a JSON tree and then read it from there? Would save a lot of reads or you could make something like a load more button, where only the first 20 results are loaded ( but this would make the user experience a little tricky and not so likable..)

Parse a local CSV with JavaScript or using Rails+JS

I have a Rails application that has some JavaScript that needs to parse CSVs and make some AJAX calls based on each record.
I'd like to just load the local CSV directly into browser memory and have the JavaScript parse it and make the required AJAX calls but I haven't found a cross-browser, dependable way to accomplish this (I need to support cruddy old IE6).
I could upload the CSV to my rails application but I plan on hosting the application on Heroku and as I understand it, Heroku doesn't allow you to edit the files system(create files). I could also write the CSVs to a database but these CSVs are large 10mb+ and I imagine I will undoubtedly suffer performance costs in doing this.
Is my best option pushing the CSV to Rails and having Rails respond with a JSON or string version of the CSV? This seems somewhat computationally expensive given the size of these CSVs. I'd prefer to keep it on the client-side. If that's the case can someone point me to an example on how to accomplish this or something similar?
Edit: I don't want users to have to copy and paste these CSVs into a textfield manually.
Edit2: Also, I'm aware of the security restrictions on accessing the local filesystem via JS. A solid flash embed is an acceptable option.

How can I iterate through files in Javascript

Is it possible to iterate through a collection of files in Javascript? I am writing a jQuery plugin that takes either an array of images or, I was hoping, a directory containing a list of images. E.g. either:
['image1.jpg','image2.jpg','image3.jpg']
or 'http://somedomain.com/images/'
I would then like to be able to iterate through the above domain and take the file name from each of the files in the folder.
I have read about the FileSystemObject but this will only be available in IE, is there an equivalent that can be used in all browsers?

You should use server side language to provide array of images in JSON or similar. There is no way Javascript can access local files. That would be serious security issue.

If the directory is on the same domain, and your webserver is setup to show directory indexes, then you could use javascript to request the url and load it into the dom for data extraction. This is brittle, and doesn't sound like it would make for a good plugin, much less good for anything but a one off task. But, you could do it.
The other suggestions of having serverside script output json or xml would be an improvement.

You can't.
You have to get the list from your server through JSON or XML. Because of this, you can't do this in any way with javascript on servers you have no control over. Also, access to client side files is actively avoided for security reasons.

You would need to create a web service to fetch the list of files. You can't use ajax to directly fetch the directory listing because ajax calls are restricted to the domain.

blogengine without php or asp.net etc

Is there a way to have a blog directly integrated into my HTML/javascript-only website, without having to have something like a SQL-database and a dynamic engine like PHP or MySQL?
Maybe there is some service in the web that offers this (hopefully without ads :) ). Or maybe I can have a blog engine entirely written in javasript?

Entirely written in JavaScript? Surely that defeats the entire point of having a "blog-engine" in the first place? The point being that the data is stored somewhere and dynamically retrieved. To avoid using anything server-side (which seems to be your intent), and only use HTML/JavaScript, you'd have to store all the data for the blog in files that are served up to each visitor, and then retrieve the data from the particular, local, locations using JavaScript.
Sorry if I'm misunderstanding the point here... but this seems to be an utterly useless way of trying to go about things. Blogs are, in general, either written statically (in HTML [even though this is rare]), or are dynamically generated from a database by a server-side scripting language (most common).
Edit: As an additional point, I suppose you could include some third-party blog feed, or service, in your page, via use of JavaScript... but I'm unsure as to which (if any) blogging services would directly support this method of working. Additionally, this is quite an unreliable way of including third-party data in a page...

Here's a thought. It's not really a blog engine - but a wiki.
Entirely javascript/html/css. All lives in a single html file:
http://www.tiddlywiki.com/
not sure how it would work on a real live site, but their site is using it:
* A personal notebook
* A GTD ("Getting Things Done") productivity tool
* A collaboration tool
* For building websites (this site is a TiddlyWiki file!)
* For rapid prototyping
* ...and much more!

You could use github pages. You will get a generated blog with version control.

Other option is to use a Desktop blog tool and then update your site.
You can user iWeb if you have a Mac or CityDesk on Windows or you may try this open source tool
Edit Today I came across this tool: Zeta producer that may help.

http://code.google.com/p/showdown-blog/
Blog engine written in just JS and XML [v0.6] {JavaScript, XML}

So, what you want is to have a blog where you're website provider doesn't provide a way to serve dynamic content?
The only way I see that you can do it in that case is writing html-files (or text-files if you prefer) and adding them to the site. After that you can have some JavaScript to add them to your "blog-page".
You of course need to upload them to the website in the same way as you do for the other files, and then have a way for the JavaScript to know which pages it should fetch.
I am not aware of any JavaScript blog-engines, but you can have a look at the templating functions in for instance Prototype
Of course, that means that you will have to fetch both the template and the content through Ajax and let the client do all the processing (could be slow and possibly insecure), and you still need to have a place to upload the content and update it.

Your best bet is going to be using a generator to create the HTML/CSS/JS to upload to your server, take a look at Webby: http://webby.rubyforge.org/

IF you really need to you can use a public api for a service that lets you post small bits of info and retrieve it using javascript.
for example if you only need small posts you can make a blog in html.javascript that utilizes twitter as the engine. of course you will be limited to 140 chars. I am sure there are other services that will allow a similar idea but with less restrictions.
And of course the best option - Get a blog software or host your blog with a service provider and link to it from you site.
Good luck

One solution would be to use some application that generates the static web pages of your blog, and uploads them to your web server. This way you'd have a blog with static content that could all be managed in javascript alongside your existing site, without needing to install database, daemon software, or additional dynamic web programming languages on your server. The static content generation could happen directly on your server if possible, or you could run the html generation tool locally and upload the output.
MoveableType has a tool like this. You still need somewhere to store the content of your blog, and for this MoveableType uses MySQL by default, so you'd still need to install a database somewhere, but the database could simply be one your local desktop.
MoveableType also has support via plugins or older versions that can retrieve data from a sqlite or other database. The advantage of sqlite is that it doesn't require installing daemons like MySQL does, you can just put a sqlite file on disk somewhere, give MoveableType the path to the file, and run the script to generate your static content.
There are likely other tools like MoveableType, and I have in the past generated blog-like web pages simply by writing small scripts to generate HTML. The main issue is just that you need somewhere for these scripts to fetch data from.
Another option might be to develop your blog using XSLT, ... with XSLT, you'd put the content of your pages in XML files, and then write a template in XSL that converts your XML to HTML.
If you google for 'static blog site generation' you might find other ideas/options, including Jekyll/github mentioned in one of the other responses.

How to parse an excel file in JavaScript?

I am trying to write a small web tool which takes an Excel file, parses the contents and then compares the data with another dataset. Can this be easily done in JavaScript? Is there a JavaScript library which does this?

How would you load a file into JavaScript in the first place?
In addition, Excel is a proprietary format and complex enough that server side libraries with years in development (such as Apache POI) haven't yet managed to correctly 100% reverse engineer these Microsoft formats.
So I think that the answer is that you can't.
Update: That is in pure JavaScript.
Update 2: It is now possible to load files in JavaScript: https://developer.mozilla.org/en-US/docs/DOM/FileReader

In the past four years, there have been many advancements. HTML5 File API has been embraced by the major browser vendors and performance enhancements actually make it somewhat possible to parse excel files (both xls and xlsx) in the browser.
My entries in this space:
http://oss.sheetjs.com/js-xls/ (xls)
http://oss.sheetjs.com/js-xlsx/ (xlsx)
Both are pure-JS parsers

To do everything in js, you'll have to use ActiveX and probably the office web components as well. Just a suggestion, but you probably don't want to go this route; it'll be inefficient and IE/Win only. You'll be better off with a server based solution.

You will need to use ActiveX (see W3C Schools on the use of AJAX) and register the file in the hosting computers Dataconnectors (only the computer hosting the file). Unlike mentioned before, this method is not Microsoft platform dependant (for the client anyways) and you do not need to have Office components installed.
This can be done for most datafiles registered in Windows, including MDB's, and allows you as much control as you want, as you can assign different Windows Accounts for different purposes.
Like I said before, this all is serverside and has no impact on the client, apart from maybe retrieving credentials, actions and all that.
This method uses JavaScript, SQL (no, not even MSSQL, just SQL standard) and requires only that the hosting computer is running ANY Microsoft NT platform.
What Windows dataconnectors do is provide a generalised interface for various data components much like DirectX does for videocards and other peripherals. You can also use it to link an MDB (Microsoft Access) to a MySQL server and feed data live that way, which I believe is even simpler than using XLS spreadsheets...especially since you can import XLS into MDB.

Do you really need an Excel file? Why not use Excel to export the data in CSV or XML and load that?
The Excel file format is very specific to Excel's implementation. If you just need the data, use a file format that just contains the data.