We Keep Coding

Can I use Google sheets as a small database for my apps?

I have a personal finances spreadsheet on my Google Drive.
For some practice and ease of use, I wanted to make a desktop and mobile app to manipulate it:
add an expense
list my expenses
filter the expenses
etc...
Is there a way to do this?
Since it is something so small, I'm trying to avoid anything that needs a dedicated server that I would need to set up or needing to rent any services because it's just a ease of use project and not a "must-have".
I've been searching a lot but most of the time I get confused with responses from 2-3 years ago.
EDIT:
So I found a way, using this video:
https://youtu.be/3OakodfKjrU
Basically using Google App Script you can make some post and get requests, which for me is a step in the right direction. Just needed to think outside of the box a little and I got a simple way to send post requests to create or update, and get requests to read, for now I also use get to delete but this just seems wrong, might change later.
Also I've searched and started doing a PWA (progressive web app) to be the interface, just so I can make it with a single code base and work with almost any device, using pure js, html and css, the only "non-pure" thing is Onsen Ui for the GUI.

You can use an NPMJS package such as google-spreadsheet to work with the Google APIs and manipulate your spreadsheet; the issue for you with trying to build the app without your own server is the need to securely store your Google Account credentials (you don't want this being publicly accessible).
If you could compromise and use a read-only solution, a package such as tabletop might suffice as you don't need to bother with any back-end work; I doubt this would be ideal for you though. You will need to host the application regardless if you want to be able to access it through the world wide web.
Alternatively, you could run the application locally if you would be happy with only being able to use the app that way. Hope it helps and sorry for the rambling!

How to change html content with URL?

I'm a beginner at coding, I know javascript but not super advanced objectd,
I'd like to know how to change html content with its URL. For example,I am on a website like GMAIL, it has different page of registring and logging in. These two pages have different URLs.
What I'd like to know is how do they change the URL along with HTML when I click on the button "Log in". Is this possible through server-side like node.js and express, or just with front-end javascript?
One last thing, do websites have multiple web pages or it's just in one single HTML file?
Well, I have set up a practice project, but I don't know what I am doing.
I changed HTML content with jQuery library but I don't know how to change URL.
First I made a homepage with some text and two links to two forms.
I showed registration form when click on "Sign in", and log in form on "Log in", and hid the homepage with the show() and hide(). The URL doesn't change in order to work with it with express. I tried it with history.pushState() but it messed up things: I can't return to homepage, and it didn't change the URL i wanted based on the form. So i deleted it, and I am stuck and don't know I could find some tutorials online.
My code doesn't contain anything other than what I described.
So, please can you explain to me how websites do that.
And one other thing, my express server now is very slow, it takes nearly 5min to start. I don't know if it's because my pc which is old and not super good unfortunately.
Can you please advice me with some tutorials and tips?

I agree that your question is too broad. Even there is many years invested in unversity to know these stuff well, I believe in self learning, so I will give you some light for your next steps in this world.
Here are some questions you may ask Google or research where ever you want:
There's both applications that hosts entire html documents in a server and reacts to http requirements responding with different ones. These are the first ones in existence.
Today the trend is to host information on distributed servers (Even cloud) as services to interact with just as information repositories, and entire client side applications that handles that information to show to the user in a more interaction friendly way.
So here are 4 first questions you can ask:
How does HTTP protocol works (with html documents e.g.)?
What's the difference between thin client and fat client applications?
What are web services?
How can I do a simple client side application with different routes using a public web service?
There is a lot of information to read about, and that's not the way I learned in university, so I can not tell you that's the right way or even a good one. Anyway, you should consider taking a web programmer beginner course, if you already know about basic algorithmic composition.
Wish you the best in this extensive path...

Wordpress to other source rest calls with username / password

I have been asked to create some custom content on a wordpress site, basically just some web app stuff (html/css/js), but leveraging data from another source via restcalls. There is a service account un/pwd required, and I am wondering what is best practice/approach in terms of the cross site calls with this un? The wire is encrypted but I certainly don't want to store the creds on the client (wordpress admin stuff). I am assuming there is a mechanism to store such on the 'back-end', filesystem, but I am not even sure such access exists? How you get to this....I have gone through the wordpress admin board and haven't found anything that provides access to the filesystem/php files, etc. Perhaps I am not looking in the right place or after the wrong bits?
I have googled but am such a noob with wordpress I am not even sure I have the right approach in mind; any help/advice is greatly appreciated.
EDIT: so if curl is the standard approach for this type of thing, where/how am I able to access the filesystem/php? Is there a specific place this type if thing lives or a convention of where it is placed? Just help with some 101 direction please.

First things first, you will need to develop a plugin for WordPress to properly hook into everything and play nice with everyone else. There are many tutorials for getting started. Here's one that integrates with an API
If you have to store things to make your plugin integrate with this third party, you should use the Options API that WP provides to you, with the information set from a settings page. Please don't hardcode that into a file somewhere in the code. (I'll also mention if you need something more powerful than the plugin options, you can add custom tables)
Now we have code running on WordPress with the information it needs, now it needs to do something. To pull the information from this third party, we can use PHP cURL.
Last, depending on how we want this information to end up being consumed by the user. We can do something simply such as just fetching/injecting the data during a regular WP page load on our custom page. Or we could be fancier and set up a WP REST API endpoint that re-serves the information we got from the 3rd party. Shortcodes? Widgets? Custom Templates? Filter Hooks? There is a lot of ways to present our final interface to the user.

Sending data SAP Fiori launchpad webapp/SAPUI5 webapp from client side javascript

This is a general question I have as I am exploring the world of automating some tasks in my workplace.
We have a portal/launchpad environment on our businesses website which has apps shown as tiles.
One of these apps when opened has a homepage that has a bunch of search fields and selectors to interface with (I assume) SAP data.
Ultimately my goal is to be able to send a number to a specific search field on a client-side local webapp (just plain old HTML/jquery stuff) and execute a search for that number in the sapui webapp.
I am getting to an competent level with javascript/HTML/CSS but am completely lost as to where to start with this type of issue as the MVC stuff is completely alien to me.
All my experience has been in creating completely client-side web apps with mostly interface with a local MS Access database.
Is what I am suggesting even possible?
So far I can open the homepage by executing the following code that someone else in the organization used:
window.open('https://fiori.mycompany.com/sap/bc/ui5_ui5/sap/z_cs_ch/index.html
Is it possible to add some form of string after a ?.... at the end of the url?
Again I am completely new to this and looking at the development guides in sapui website isn't shedding any light on it either. Possibly because I don't really know exactly what I am looking for!
Any help /guidance is greatly appreciated.
EDIT:
After comments below I can see the request sent to server is in the following format:
Request GET /sap/opu/odata/sap/someotherlocation/SearchTerm('<variable to search for>')?$format=json HTTP/1.1
Am I right in thinking I could potentially send an ajax request to do something similar? If so, how do I go about it?
Thanks again

There are possibilties to achieve that but i think it's not a real good solution, to fill fields in another web application and to trigger the search.
It would be better if you know the backend service which is used by this Fiori App, and to integrate directly the service. If it's an Fiori App i might be an OData /REST Service. Odata/REST Service also can be called by HTML/jquery JavaScript stuff too.
In order to determine the Service URL and the payload which is used by the web app with the search field, just use Chrome Debugger Tools (or other Browser Debug Tools) and check under Network which server address and which payload parameters are sent to the server, when you trigger the search manually. Hope that helps you little bit.

In the whole Fiori concept, it is definitely possible to have applications to call other applications and to get them to open up exactly at the point the user expects it. E.g. from a order click on a product to be brought to the material master, and have the material master app exactly show the product the user clicked on.
As you mentioned, this would indeed require the target application (that is navigated to) to support some parameters. You mentioned in your question already that you wondered if it would be possible to add a "?...." section to the URL. Fiori apps definitely support this concept, but how it is implemented depends very much on the app itself. In my previous example it could be as easy as e.g. adding ?product_id=abcde though.
Fiori also has very nice extensibility concepts built-in. So if your target app doesn't exactly support the parameters you intend to pass, you could easily extend the app to support it, without having to rewrite of copy the entire app (which would be a disaster when you receive updated from the original developer).
To navigate from one Fiori app to the other, it is advised to use the toExternal method of the CrossApplicationNavigation service, which comes with the Fiori launchpad. This service allows you to specify parameters such as the app you'd like to navigate to, the intent (display, create etc), parameters (such as product ID) and a app specific route (e.g. /supplierdetails to see the supplier details of a product).
The CrossApplicationNavigation service is officially documented in the SAPUI5 SDK, but I'm afraid that the SDK doesn't contain a very elaborate description. However, if you Google for it, you'll find extensive information and examples on SCN and Stackoverflow on this topic as well.

As promised here is what I got to work - actually got the overall method from an answer on here somewhere else.
This will send back enough detail that I can at least show the user some updates however after searching around I believe what I really need to be able to do is batch requests... I'm looking into Apache Olingo to see if that's possible.
function orderSmmary(SO) {
var uri = "https://fiori.<company>.com/sap/opu/odata/sap/<environment>/Details('"+ SO + "')?$format=json";
var http_request = new XMLHttpRequest();
http_request.onreadystatechange = function() {
if (http_request.readyState == 4 ) {
var data = JSON.parse(http_request.responseText);
// Do lots of awesome stuff with response
}
}
http_request.open('GET',uri, true);
http_request.setRequestHeader("Authorization", "Negotiate");
http_request.send();
}
Again this is an entirely clientside solution from completely outside any flori environment so I am hoping to stay completely javascript based.

Scrape gmail for the last time external pop accounts were checked and check them if longer than X time since the last check

Goal:
To develop an script that will check the last time my external pop accounts were checked by google -- while not being logged in. If the time exceeds some amount, then check the pop account.
My Reason:
I use an offline client. I don't want to be logged into gmail and I want all my external emails to flow thru gmail. Sometimes an important email comes in and I have to log into gmail, go to the account section, and then click "check email". This is incredibly annoying. I wish they had the ability to poll for pop account at a specified frequency. Instead they use an algorithm that can range from 1 minute to 1 hour.
My Approaches so far:
So I can log into gmail using curl. I can scrape the pages. The problem is that google uses javascript/ajax goodness so curl does gets the html version of gmail and that version does not have the info that I am looking for. It's only available on the ajax version of gmail.
I can use selenium, but essentially I have to have firefox open. I don't want that. I want a solution that can run in the background that will check every 10 minutes.
My suspicions on how to go about this:
I've seen several posts about using headless browsers with javascript capabilities. Apparently some of these can be controlled using python. However, this seems quite complicated.
Thus, my questions
What is the best way to solve my problem? My preference is to use python, but I am open to other languages as well. Will I have to use javascript to accomplish this task? Is a headless browser necessary or are there other alternatives?
Thank you.

Probably http://www.phantomjs.org/ is going to be the best tool for this job. They have lots of examples in their github repository for how to do this type of thing. People have had good success with complex scraping tasks.