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How to get previous route - route from where i came to current page

There are different ways through which I know the current route in angular.
I would like to know the previous route. Say for example im in a tab http://localhost:4200/test/testNav/ABC
Now, i click another tab that takes me to
http://localhost:4200/test/SampleNav/XYZ
In the ngOnInit() method of this html "http://localhost:4200/test/SampleNav/XYZ" i want to get the previous url which is /ABC.
this.router.url, this.activatedRoute.snapshot all gives me the currenturl. Is there a way to get the previous url from the available angular components.
Basically when I come to XYZ page from ABC i should do something and when I come to XYZ from CBA i should do something else. Any inputs highly appreciated.

Here comes getCurrentNavigation() used with optional chaining (question mark) because it can be null. There you can take previousNavigation and finalUrl will return you an UrlTree. Next just execute navigation on finalUrl if it is not null.
const urlTree = this.router.getCurrentNavigation()?.previousNavigation?.finalUrl;
if (urlTree) {
this.router.navigateByUrl(urlTree);
}

How to get the modified content from google sheets?

I am trying to get the modified content after the given time from google sheets. Nowhere I can found the api to get the data. What i can see is getting modified date alone from the drive Api. How can I get the data using Drive or Sheets Api? Give me the suggestions if Possible

Google Drive keeps a track of revision history of files that are contained on it. There is however, no way to obtain the revisions from a request alone.
Google allows for you to receive email notifications whenever a user makes an edit to your sheet, which you can set up by completing the following steps:
In the Spreadsheet's web view, click Tools -> Notification rules...
Under Notify me at myemail#address.ext when... select Any changes are made
Under Notify me with... select Email - right away
Click Save.
You should also be aware that you will not get a notification for edits made to the sheet by you - notifications are only received when another user edits the sheet. Whenever you get an email notification, you will receive a link to view the changes to the spreadsheet in the form of a read-only web view link.
You can work around this programatically, though there isn't one right way and it can be quite complicated. You can use the Revisions: list method of the Drive REST API to get the information about the user that made an edit, as well as a list of links which you can use to export that revision of the sheet to another MIME Type, as shown below in the request response.
Requesting:
GET https://www.googleapis.com/drive/v3/files/SPREADSHEET_ID/revisions
with revisions/exportLinks,revisions/lastModifyingUser/emailAddress as the fields field and replacing SPREADSHEET_ID with the ID of the spreadsheet will give you a 200 response:
{
"revisions": [
{
"lastModifyingUser": {
"emailAddress": "username#domain.ext"
},
"exportLinks": {
"application/x-vnd.oasis.opendocument.spreadsheet": "https://docs.google.com/spreadsheets/export?id=SPREADSHEET_ID&revision=revisionNumber&exportFormat=ods",
"text/tab-separated-values": "https://docs.google.com/spreadsheets/export?id=SPREADSHEET_ID&revision=revisionNumber&exportFormat=tsv",
"application/pdf": "https://docs.google.com/spreadsheets/export?id=SPREADSHEET_ID&revision=revisionNumber&exportFormat=pdf",
"application/vnd.openxmlformats-officedocument.spreadsheetml.sheet": "https://docs.google.com/spreadsheets/export?id=SPREADSHEET_ID&revision=revisionNumber&exportFormat=xlsx",
"text/csv": "https://docs.google.com/spreadsheets/export?id=SPREADSHEET_ID&revision=revisionNumber&exportFormat=csv",
"application/zip": "https://docs.google.com/spreadsheets/export?id=SPREADSHEET_ID&revision=revisionNumber&exportFormat=zip",
"application/vnd.oasis.opendocument.spreadsheet": "https://docs.google.com/spreadsheets/export?id=SPREADSHEET_ID&revision=1&exportFormat=ods"
}
}
]
}
With the links to individual changes, you can fetch and compare the different versions of the Sheet using Apps Script, and output A1 notation of the cells that have different values between versions. This, with the email address from the original Revisions: list request, is enough to compile a file or a log containing.
You can put this into a simple onEdit() trigger bound to the sheet will allow you to automatically get the changes each time a user edits the sheet.

JavaScript EJB variable field holding value?

I have an ajax enabled list of records that I'm going through and each one has a dropdown box that I'm trying to make a required field for the form to submit. To complicate matters the 'Close Record' button is not the submit button so I can't just use required attribute on the select(dropdown box) that I'm using. The value for the selected dropdown box is saved in an Enterprise Java Bean so I thought I could just write a JavaScript function to check the value:
function CheckForm() {
var clearObj = document.getElementById("mySelect");
if(clearObj.value != "") {
return true;
} else {
clearObj.style.backgroundColor ='yellow';
}
return false;
}
This doesn't work because once I close one and go to the next it's maintaining the value of the previous record on the page. Basically I have an update-content event that I need to know how to handle. Any ideas as to how to manipulate the DOM or JSON object to make this select a required field? Thanks.

With the little information given, I would assume that when you close the existing record and then loading the next record, you are doing it through an ajax request. If thats the case, then you can add a call back for the ajax request, which would reset the drop down.
This should be a comment, but as you see, I dont have 50 points :-)

how to forward back to JSP page without losing the data entered in fields?

I have a simple MVC-based JSP application. Something like:
*.jsp -> ControllerServlet -> *Command.java -> *Service.java -> *DAO.java -> Oracle db
A typical link in the application looks like this:
myapp/controller?cmd=ShowEditUser&userid=55
Which causes ShowEditUserCommand.java execute() method to run and will forward to editUser.jsp
In editUser.jsp, they fill in the fields, then click Save which posts to myapp/controller?cmd=ModifyUser which runs ModifyUserCommand.java execute() method which modifies the user data and forwards to viewUser.jsp.
Everything works fine.
The problem is, in ModifyUserCommand.execute() I'm checking to see if the username is unique. If they try to enter a username that already exists, I set an error value to true and errorMessage value to Already in use.
Then because of the error I forward to the original editUser.jsp (not viewUser.jsp) and the error is displayed above the form.
MY PROBLEM IS (finally! ;) -- when the user is returned to editUser.jsp with the error message displayed, the data they entered in the fields is all blanked out. How can I set it so whatever they entered in the fields is still in place?
Any suggestions or advice are greatly appreciated!
Rob

Simplest way would be to pass the form fields back to your editUser.jsp in your forward action in ModifyUserCommand.execute(). You can do that with individual parameters i.e.
editUser.jsp?field1=1&field2=2
Alternatively, you could pass data with other methods - i.e. encoded JSON.
You can then process your fields in your editUser.jsp via the page's request object and set your form field values accordingly.
There may be other ways to do this depending on what underlying framework (if any) you are using. But this is a basic way of approaching it.

what is the best way to display website visitors a one time welcome message?

I've got a website, and I want to add a welcoming message which hovers on a certain part of the page which only loads for the visitor for the first time they login, and won't again(presumably cookies used). And says something like "adjust your settings here.."
I don't want it to be an external popup but something that loads on the page in a certain area, defined by me (PX-pixle reference)
What would be the best coding language to do it in, oes anyone have any examples of this, or any site based generators to make it on?
thanks

Create one more field in database with lastlogin.
When user is created then make lastlogin field with special.
When user signs the next time from Login Page, update the field the lastlogin value to regular
//query to get value of lastlogin
//add css to elements you want to hover
<element class="<?php if($last-login == 'sepcial') { echo 'sepcialcss'; } else {echo 'regularcss'; }">
Done in PHP

As you added the tag, php would do this, actually any language will do.
Generally you have two ways to do this.
Do it on your server.
Do it on client's computer.
for the first way, you check the cookies and generate the page you want.
for the second way, you need to arrange the page the visitors see with java script.
way 1 recommended, coz it loads less bits. LOL
Update:
your server supports php right? the page, say it index.php, has a special area which is different when the visitors login the first time, right?
<?php
if (firstLogin()){
genSpecial();
}
else{
genRegular();
}
?>
in the funcition firstLogin(), you shall read the cookies and determine.
in the other two functions, just gen two different part, i.e. some html source code.
to your question, if you need to load some image, do it in genSpecial(). and if you choose the first way, js is not used to gen the special area, it's used only if in the special area, there needs some js.

It is possible through javascript. Once the user is shown the settings, store the result in a cookie valid for as long as you want. The next time the user logs in, verify if the cookie is set and then proceed.
Sample code to create cookies:
function setCookie(c_name,value,exdays)
{
var exdate=new Date();
exdate.setDate(exdate.getDate() + exdays);
var c_value=escape(value) + ((exdays==null) ? "" : "; expires="+exdate.toUTCString());
document.cookie=c_name + "=" + c_value;
}
Refer this for more details on how to create and use cookies