React-admin pagination count number is not correct - javascript

I have found solution for pagination to take N elements per page
BUT the i don't found solution or documentation to get count number of pages.
is incorrect ,
PLS help

It is probable that your dataProvider.getList() doesn't return the correct total. The expected response format should be:
{ data: record[], total: number }
Where total is the total number excluding pagination (i.e. if you have a pagination of 10, but the query has 150 results, total should be 150 on every page).
See https://marmelab.com/react-admin/DataProviderWriting.html#example-rest-implementation for more information.

Related

Trying to write a basic script for a Google Sheets that will count total missed minutes by late students

I am (VERY) new to Apps Script and JS generally. I am trying to write a script that will automatically tally the difference between student entry time and start time of a course to deliver total minutes missed.
I have been able to get a function working that can do this for a single cell value, but am having trouble iterating it across a range. Doubtless this is due to a fundamental misunderstanding I have about the for loop I am using, but I am not sure where to look for more detailed information.
Any and all advice is appreciated. Please keep in mind my extreme "beginner status".
I have tried declaring a blank variable and adding multiple results of previously written single-cell functions to that total, but it is returning 0 regardless of given information.
I am including all three of the functions below, the idea is that each will do one part of the overall task.
function LATENESS (entry,start) {
return (entry-start)/60000
}
function MISSEDMINUTES(studenttime,starttime) {
const time = studenttime;
const begin = starttime;
if (time=="Present") {
return 0
} else if (time=="Absent") {
return 90
} else {
return LATENESS(time,begin)
}
}
function TOTALMISSED(range,begintime) {
var total = 0
for (let i = 0; i < range.length; i++) {
total = total + MISSEDMINUTES(i,begintime)
}
}```
If you slightly tweak your layout to have the 'missing minutes' column immediately adjacent to the column of names, you can have a single formula which will calculate the missing minutes for any number of students over any number of days:
Name
*
2/6
2/7
2/8
2/9
John Smith
-
Present
Present
Absent
10:06
Lucy Jenkins
-
Absent
Absent
Absent
Absent
Darren Polter
-
Present
Present
Present
10:01
With 'Name' present in A1, add the following to cell B1 (where I've marked an asterisk):
={"mins missed";
byrow(map(
C2:index(C2:ZZZ,counta(A2:A),counta(C1:1)),
lambda(x,switch(x,"Present",0,"Absent",90,,0,1440*(x-timevalue("10:00"))))),
lambda(row,sum(row)))}
We are MAPping a minute value onto each entry in the table (where 'Present'=0, 'Absent'=90 & a time entry = the number of minutes difference between then and 10am), then summing BYROW.
Updated
Based on the example, you could probably have a formula like the below one to conduct your summation:
=Sum(ARRAYFORMULA(if(B2:E2="Absent",90,if(isnumber(B2:E2),(B2:E2-$K$1)*60*24,0))))
Note that k1 has the start time of 10:00. Same sample sheet has working example.
Original Answer
I'm pretty sure you could do what you want with regular sheets formulas. Here'a sample sheet that shows how to get the difference in two times in minutes and seconds... Along with accounting for absent.
Here's the formula used that will update with new entries.
=Filter({if(B2:B="Absent",90*60,Round((C2:C-B2:B)*3600*24,0)),if(B2:B="Absent",90,Round((C2:C-B2:B)*3600*24/60,1))},(B2:B<>""))
This example might not solve all your issues, but from what I'm seeing, there's no need to be using an app script. If this doesn't cover it, post some sample data using Mark down table.

Simple popular/trending products algorithm for an ecommerce site with Javascript

I am currently building a small ecommerce site and for the home page, I would like to rank the products based on popularity. The product schema has the following data:
{
...
noViews: Number, // Number of times a user has clicked on the product
avgRating: Number, // Average star rating (1 - 5)
datePosted: Date // Date the product was posted
}
What is a (relatively) simple algorithm/code I can use to implement this (with Node.js), where the products would be ranked based on popularity (with time taken into consideration so the content isn't stale).
Thank you.
First of all, you need a time based metric to solve this.
Overall trending products does not make much sense particularly for a ecommerce app.
Lets say, you want to do find the trending products for a particular day (say today).
Now this is not a easy problem to solve. And there is no just 1 direct way to solve it. For each company, one method works!
Ideally , what could be a simple solution here would be to create a score value based on combination of factors. For example, number of buys, number of views, number of clicks and so on.
Here, you have the datePosted parameter. Now, create a date_score for this. So, the basic idea here is a product that was posted yesterday has more score than the one posted a week back. The values you put need to tweaked and checked for your algorithm's customization.
Similarly, implemeent a similar score for avgRating and noViews.
Once you have these scores ready, create weights for these scores. Now the weighted average for these out of 100 is the final score.
So, a final example solution:
Date Posted:
If Date is in the last 3 days (score = 100)
If Date is the last week (score= 75)
If Date in the previous week (score = 50)
Else default score = 25.
Star Rating:
(Rating/5 ) *100
numberOfViews:
Here , you can use percentiles.
Lets say max views among all the product is x.
Then, the view score is (views/x) *100
Now, handle the corner case of what happens when two scores match.
After this, you can simply order by the score parameter.
Also, make sure everything you do is dynamic as static thresholds dont provide a great resul generally!

undertanding javascript pagination math problem

I am trying to understand how to approach math problems such as the following excerpt, which was demonstrated in a pagination section of a tutorial I was following.
const renderResults = (arrayOfItems, pageNum = 1, resultsPerPage = 10) => {
const start = (pageNum - 1) * resultsPerPage;
const end = pageNum * resultsPerPage;
arrayOfItems.splice(start, end).forEach(renderToScreenFunction);
};
In the tutorial this solution was just typed out and not explained, which got me thinking, had I not seen the solution, I would not have been able to think of it in such a way.
I understood the goal of the problem, and how splice works to break the array into parts. But it was not obvious to me how to obtain the start and end values for using the splice method on an array of of indefinite length. How should have I gone about thinking to solve this problem?
Please understand, I am learning programming in my spare time and what might seem simple to most, I have always been afraid and struggle with math and I am posting this question in hopes to get better.
I would really appreciate if anyone could explain how does one go about solving such problems in theory. And what area of mathematics/programming should I study to get better at such problems. Any pointers would be a huge help. Many thanks.
OK, so what you're starting with is
a list of things to display that's, well, it's as long as it is.
a page number, such that the first page is page 1
a page size (number of items per page)
So to know which elements in the list to show, you need to think about what the page number and page size say about how many elements you have to skip. If you're on page 1, you don't need to skip any elements. What if you're on page 5?
Well, the first page skips nothing. The second page will have to skip the number of elements per page. The third page will have to skip twice the number of elements per page, and so on. We can generalize that and see that for page p, you need to skip p - 1 times the number of elements per page. Thus for page 5 you need to skip 4 times the number of elements per page.
To show that page after skipping over the previous pages is easy: just show the next elements-per-page elements.
Note that there are two details that the code you posted does not appear to address. These details are:
What if the actual length of the list is not evenly divisible by the page size?
What if a page far beyond the actual length of the list is requested?
For the first detail, you just need to test for that situation after you've figured out how far to skip forward.
Your function has an error, in the Splice method
arrayOfItems.splice(start, end).forEach(renderToScreenFunction);
The second argument must be the length to extract, not the final
index. You don't need to calculate the end index, but use the
resultsPerPage instead.
I've rewrite the code without errors, removing the function wrapper for better understanding, and adding some comments...
// set the initial variables
const arrayOfItems =['a','b','c','d','e','f','g','h','i','j','k','l','m'];
const pageNum = 2;
const resultsPerPage = 5;
// calculate start index
const start = (pageNum - 1) * resultsPerPage; // (2-1)*5=5
// generate a new array with elements from arrayOfItems from index 5 to 10
const itemsToShow = arrayOfItems.splice(start, resultsPerPage) ;
// done! output the results iterating the resulting array
itemsToShow.forEach( x=> console.log(x) )
Code explanation :
Sets the initial parameters
Calculate the start index of the array, corresponding to the page you try to get. ( (pageNum - 1) * resultsPerPage )
Generates a new array, extracting resultsPerPage items from arrayOfItems , starting in the start index (empty array is returned if the page does not exist)
Iterates the generated array (itemsToShow) to output the results.
The best way to understand code, is sometimes try to run it and observe the behavior and results.

How to get the right page count?

I am new to JavaScript, I want to get the right page count.
if one page the item count is 20, and the page count is 23, the page should be 2.
var count = 23
var per_page_count = 20
If in other language we can use:
count / per_page_count + 1
to get the page count, but in JavaScript we can not get it.
I also tried use Math.round, still not work
console.log(Math.round(count/per_page_count)) // there I want to get 2, but get 1
You can use
Math.ceil(count/per_page_count)
The Math.ceil() function returns the smallest integer greater than or equal to a given number.
from Math.ceil document.
I think you are trying to implement some sort of pagination. So I would suggest :
Maths.ceil(count/per_page_count)

Calculate percentile rank (Parse)

I need to calculate the percentile rank of a particular value against a large number of values filtered in various different ways. The data is all stored on Parse.com, which has a limitation of returning a maximum of 1000 rows per query. The number of values stored is likely to exceed well over 100,000.
By 'percentile rank', I mean I need to calculate the percentage of values that the provided value is greater than. I am not trying to calculate the value of a provided percentile. For example, given a list of values {20, 23, 24, 29, 30, 31, 35, 40, 40, 43} the percentile rank of the provided value 35 is 70%. The algorithm for this is simply the rank of the value / count of values * 100. Not sure if 'percentile rank' is the correct terminology for this.
I have considered a couple of different approaches to this. The first is to pull down the full list of values (into Parse Cloud) and then calculate the percentile rank from there, then filter the list and calculate again, repeating the last two steps as many times as required. The problem with this approach is it will not work once we reach 1000 values, which we can expect pretty quickly.
Another option, which is the best I can come up with so far, is to query the count of items, and the rank of the provided value. For example:
var rank_world_alltime = new Parse.Query("Values")
.lessThan("value", request.params.value) // Filters query to values less than the provided value, so counting this query will return the rank
.count();
var count_world_alltime = new Parse.Query("Values")
.count();
Parse.Promise.when(rank_world_alltime, count_world_alltime).then(function(rank, count) {
percentile = rank / count * 100;
console.log("world_alltime_percentile = " + percentile);
});
This works well for a single calculation, but I need to perform multiple calculations, and this approach very quickly becomes a lot of queries. I expect to need to run about 15 calculations per call, which is 30 queries. All calculations need to complete in under 3 seconds before Parse terminates the job, and I am limited to 30 reqs/second, so this is very quickly going to become a problem.
Does anyone have any suggestions on how else I could approach this? I've thought about somehow pre-processing some of this but can't quite work out how to do so, as the filters will be based on time and location (city and country), so there are potentially a LOT of pre-calculations that will need to be run at regular intervals. The results do not need to be 100% accurate but something close.
I don't know much about parse, but as far as I understand what you say, it is some kind of cloud database thingy that holds your hiscores, and limits you 1000 rows per query, 3 seconds per job, and 30 queries per second.
In order to have approximate calculations and divide by 2 the number of queries, I would first of all cache the total (count_world_alltime, count_region,week, whatever). If you can save them somewhere locally. For numbers of 100K just getting the order of magnitude (thus not the latest updated number) should be good enough to get a percentile.
Maybe you can get several counts per query. However my lack of expertise in parse/nosql kind of stops me from being sure of this, you'll have to check their documentation. If it is possible however, for the case where you need percentiles for a serie of values all in the same category, I would
Order the values, let's call them a,b,c,d,e (once ordered)
Get the number of values between the intervals [0,a] [a,b] [b,c] [c,d] [d,e]
Use the cached total to get the percentiles (where Nxy is the number of values in [x,y]) :
Pa = 100 * N0a / total
Pb = 100 * ( N0a + Nab ) / total
Pc = 100 * ( N0a + Nab + Nbc ) / total
and so on...
If you need a value ranked worldwide, the other per region, some per week others over all times, etc, this doesn't apply. In that case I don't think you can get below 1 query/number, with caching the totals.

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