51 lines
1.4 KiB
JavaScript
51 lines
1.4 KiB
JavaScript
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var baseRandom = require('../internal/baseRandom'),
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isIterateeCall = require('../internal/isIterateeCall'),
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toArray = require('../lang/toArray'),
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toIterable = require('../internal/toIterable');
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/* Native method references for those with the same name as other `lodash` methods. */
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var nativeMin = Math.min;
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/**
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* Gets a random element or `n` random elements from a collection.
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*
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* @static
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* @memberOf _
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* @category Collection
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* @param {Array|Object|string} collection The collection to sample.
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* @param {number} [n] The number of elements to sample.
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* @param- {Object} [guard] Enables use as a callback for functions like `_.map`.
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* @returns {*} Returns the random sample(s).
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* @example
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*
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* _.sample([1, 2, 3, 4]);
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* // => 2
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*
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* _.sample([1, 2, 3, 4], 2);
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* // => [3, 1]
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*/
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function sample(collection, n, guard) {
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if (guard ? isIterateeCall(collection, n, guard) : n == null) {
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collection = toIterable(collection);
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var length = collection.length;
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return length > 0 ? collection[baseRandom(0, length - 1)] : undefined;
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}
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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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n = nativeMin(n < 0 ? 0 : (+n || 0), length);
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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 = sample;
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