react-native/Libraries/Utilities/groupByEveryN.js

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/**
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @format
* @flow strict
*/
/**
* Useful method to split an array into groups of the same number of elements.
* You can use it to generate grids, rows, pages...
*
* If the input length is not a multiple of the count, it'll fill the last
* array with null so you can display a placeholder.
*
* Example:
* groupByEveryN([1, 2, 3, 4, 5], 3)
* => [[1, 2, 3], [4, 5, null]]
*
* groupByEveryN([1, 2, 3], 2).map(elems => {
* return <Row>{elems.map(elem => <Elem>{elem}</Elem>)}</Row>;
* })
*/
'use strict';
function groupByEveryN<T>(array: Array<T>, n: number): Array<Array<?T>> {
const result = [];
let temp = [];
for (let i = 0; i < array.length; ++i) {
if (i > 0 && i % n === 0) {
result.push(temp);
temp = [];
}
temp.push(array[i]);
}
if (temp.length > 0) {
while (temp.length !== n) {
temp.push(null);
}
result.push(temp);
}
return result;
}
module.exports = groupByEveryN;