50 lines
1.3 KiB
JavaScript
50 lines
1.3 KiB
JavaScript
var baseClamp = require('./_baseClamp'),
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baseRandom = require('./_baseRandom'),
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isIterateeCall = require('./_isIterateeCall'),
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toArray = require('./toArray'),
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toInteger = require('./toInteger');
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/**
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* Gets `n` random elements at unique keys from `collection` up to the
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* size of `collection`.
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*
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* @static
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* @memberOf _
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* @since 4.0.0
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* @category Collection
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* @param {Array|Object} collection The collection to sample.
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* @param {number} [n=1] The number of elements to sample.
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* @param- {Object} [guard] Enables use as an iteratee for methods like `_.map`.
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* @returns {Array} Returns the random elements.
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* @example
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*
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* _.sampleSize([1, 2, 3], 2);
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* // => [3, 1]
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*
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* _.sampleSize([1, 2, 3], 4);
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* // => [2, 3, 1]
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*/
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function sampleSize(collection, n, guard) {
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var index = -1,
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result = toArray(collection),
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length = result.length,
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lastIndex = length - 1;
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if ((guard ? isIterateeCall(collection, n, guard) : n === undefined)) {
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n = 1;
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} else {
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n = baseClamp(toInteger(n), 0, length);
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}
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while (++index < n) {
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var rand = baseRandom(index, lastIndex),
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value = result[rand];
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result[rand] = result[index];
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result[index] = value;
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}
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result.length = n;
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return result;
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}
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module.exports = sampleSize;
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