Calculating item offset for pagination

Question

this seems like very simple maths but somehow, my brain cant think ...

i am trying to implement pagination and will need to calculate the item offset to use in limi

Answer 1

Using JS as an example, for progressive web app people...

JS arrays have the prototype method .slice(start, end) overview here it takes a start index and an end index as arguments.

I found the easiest way to calc both indexes is as follows;

Start Index

var start =  parseInt((selectedPage - 1) * resultsPerPage);

End Index

var end = parseInt(selectedPage * resultsPerPage);

Execution

var myPaginatedArray.slice(start, end);

Answer 2

Use offset = (page - 1) * itemsPerPage + 1.

Answer 3

Honestly depends. I'm no PHP person, but I'll put both out there. If you are pulling your records in to some form of collection (list, array, etc.) then your formula should be:

offset = (page - 1) * itemsPerPage

This is because most (again, I'm not a PHP person) arrays and lists use 0 for their first element. If they do not use 0 for their first element and/or you're pulling from a table or something else where the IDs start at 1, then it should be:

offset = (page - 1) * itemsPerPage + 1

I hope that's clear and helps.