Questions




Answers
1
Error "TypeError: Cannot read property 'classList' of null"

Hello, I am trying when simple code to add datepicker in javascript using below HTML and Javascript Code, but I am getting error "TypeError: Cannot read property 'classList' of null", how can I resolve it?

cannot-read-properties-of-null-reading-classlist-min_sgpbi5.png

HTML/JS Code

...
Read More
Answers
1
What difference does checkpointing makes in log based recovery?

This is more of a big data question(GFS related). I'm not getting how checkpointing help? Can you share 1 example(which could be DBMS example).

Say these are the operations on the database.

...
Read More
Answers
1
Get only time from Datetime in C#?

Hello, I was checking this How to show date time with am/pm using C# in ASP.NET? but I would like to know simple C# code to get only time from datetime in C#.  So for example, If I have  ' 09/04/2022 03:52 PM', i need only '03:53 PM'.

...
Read More
Answers
1
Why did we remove multiple document types within an index in ElasticSearch?

The answer is this-: Because we can't declare a field of different data types within a same index in different document types.

Say there's an index called "college".

Then there are document types called "student" "teacher" "administration" "staff".

What problem would occur if we allow this? 

Books and documentations are saying that if a field called "date_of_join" is given a "text" data type in "student", then we can't give "date_of_join" as "date" data type in "staff".

It says that it's due to the way Lucene is.

This is because of the way Lucene maintains the field types in an index. As Lucene manages fields on an index level, there is no flexibility to declare two fields of different data types in the same index

But this is not clear without an example(of how lucene is storing index). Can you guys clarify this? 

I know that lucene stores inverted indexes though. But still I'm not clear.

...
Read More
Answers
1
How to add time in datetime in C#?

Hello, If I have a time string "4:49 pm" or timespan value and I would like to add it in a datetime value, how can i do it in C#?

...
Read More
Answers
1
How to detect click outside an element (or div)?

Hello, I am trying to work on a project which requires me not allow a user to click outside of a particular element, let's say a "<div>" or "<p>", then how can I detect click outside an element using Javascript?

...
Read More
Answers
1
How to add authorization header in postman?

Hello, I have read this post Upload or Send File in Postman but now I want to add authorization token also, before sending request in Postman? So how can I add authorization header in postman? I have generated token using simply GET request.

...
Read More
Answers
1
How does Content Delivery Network works (from web dev point of view)?

I find it simple. Have a CDN edge server near the user, cache the request and when next time he asks for it, give it. But I am pretty sure what I am thinking, although correct, isn't complete and there is something missing.

My book has just included some small benefits of CDN, that's all. But that too isn't given in detail with illustrations(although it is not necessary i feel). Exam questions of mine has asked like how CDN reduces delay in received requested object for 8 marks(3hrs exam, 80 full marks).

The answer to this is literally 1 line ie the definition of CDN. and maybe 2 figures showing how it works with and without CDN. another question asked in the exam is-: how proxy CDN works, explain with example.

I am not sure how the updating of content happens.

Does only 1 proxy server gets updated or do all proxy servers get updated when 1 CDN brings a fresh copy of the web page from the origin server? It is confusing; believe me, the tutorials for this thing are advertisements for various CDNs.

...
Read More
Answers
1
AJAX request confusion

Figure i am talking about-:

https://imgur.com/a/T4viIKF

 

Confusions, "ie" means my interpretation that i am not sure if is correct or not)-:

1) user clicks invoking an event handler.

  i.e when an user event occurs, it makes a javascript call. most likely user event=function call

2) handler's code creates xmlhttprequest object

  i.e that javascript call creates xmlhttprequest in ajax engine.

3) xhr requests file from server

4) server sends the file.

5) NOW I AM CONFUSED.

the terminologies are confusing me. 

like-:

  1. a) xhr fires an event. what does that mean? and why to fire an event? Doesn’t user only fire event? Like clicking,pressing some key etc.
  2. b) you can attach handler function to event. (maybe it is trying to talk about event handler i.e if event->handlerfunction() )..I am not sure. 

handler fxn then processes the data and displays it.

...
Read More
Answers
1
Error Code: 1175 - You are using safe update mode

When I am trying to execute this query in MySQL Workbench 'DELETE FROM Job;', I am getting below error 

Error Code: 1175. You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column. To disable safe mode, toggle the option in Preferences -> SQL Editor and reconnect.

So, how can I resolve this error, why I cannot Execute the simple delete query?

...
Read More

Page 1 of 51