EN
JavaScript - how to calculate page number when we know size of page and item index?
2
points
In this article, we're going to have a look at how in JavaScript, calculate page number on which is item when we know:
- size of page,
- item index.
Simple example:
// ONLINE-RUNNER:browser;
function calculatePageNumber(pageSize, itemIndex) {
return Math.ceil(++itemIndex / pageSize);
};
// Example usage:
var pageSize = 10;
var itemIndex = 29;
var pageNumber = calculatePageNumber(pageSize, itemIndex);
console.log('pageNumber=' + pageNumber); // 3
// Result explanation:
// page 1 -> indexes from 0 to 9
// page 2 -> indexes from 10 to 19
// page 3 -> indexes from 20 to 29
// etc.
Example tests:
// ONLINE-RUNNER:browser;
function calculatePageNumber(pageSize, itemIndex) {
return Math.ceil(++itemIndex / pageSize);
};
// Exmaple tests:
var pageSize = 10;
var testingData = [
{ itemIndex: 0, expectedPagesNumber: 1 },
{ itemIndex: 1, expectedPagesNumber: 1 },
{ itemIndex: 9, expectedPagesNumber: 1 },
{ itemIndex: 10, expectedPagesNumber: 2 },
{ itemIndex: 11, expectedPagesNumber: 2 }
];
for (var i = 0; i < testingData.length; ++i) {
var entry = testingData[i];
var expected = entry.expectedPagesNumber;
var actual = calculatePageNumber(pageSize, entry.itemIndex);
var print = (expected === actual ? console.log : console.error);
print(expected + ' === ' + actual);
}