es-toolkit/dist/array/sampleSize.js

A state-of-the-art, high-performance JavaScript utility library with a small bundle size and strong type annotations.

const require_randomInt = require("../math/randomInt.js");
//#region src/array/sampleSize.ts
/**
* Returns a sample element array of a specified `size`.
*
* This function takes an array and a number, and returns an array containing the sampled elements using Floyd's algorithm.
*
* {@link https://www.nowherenearithaca.com/2013/05/robert-floyds-tiny-and-beautiful.html Floyd's algorithm}
*
* @template T - The type of elements in the array.
* @param array - The array to sample from.
* @param size - The size of sample.
* @returns A new array with sample size applied.
* @throws {Error} Throws an error if `size` is greater than the length of `array`.
*
* @example
* const result = sampleSize([1, 2, 3], 2)
* // result will be an array containing two of the elements from the array.
* // [1, 2] or [1, 3] or [2, 3]
*/
function sampleSize(array, size) {
	if (size > array.length) throw new Error("Size must be less than or equal to the length of array.");
	const result = new Array(size);
	const selected = /* @__PURE__ */ new Set();
	for (let step = array.length - size, resultIndex = 0; step < array.length; step++, resultIndex++) {
		let index = require_randomInt.randomInt(0, step + 1);
		if (selected.has(index)) index = step;
		selected.add(index);
		result[resultIndex] = array[index];
	}
	return result;
}
//#endregion
exports.sampleSize = sampleSize;