30 lines
1008 B
JavaScript
30 lines
1008 B
JavaScript
var _isArrayLike = require('./_isArrayLike.js');
|
||
var values = require('./values.js');
|
||
var _getLength = require('./_getLength.js');
|
||
var random = require('./random.js');
|
||
var toArray = require('./toArray.js');
|
||
|
||
// Sample **n** random values from a collection using the modern version of the
|
||
// [Fisher-Yates shuffle](https://en.wikipedia.org/wiki/Fisher–Yates_shuffle).
|
||
// If **n** is not specified, returns a single random element.
|
||
// The internal `guard` argument allows it to work with `_.map`.
|
||
function sample(obj, n, guard) {
|
||
if (n == null || guard) {
|
||
if (!_isArrayLike(obj)) obj = values(obj);
|
||
return obj[random(obj.length - 1)];
|
||
}
|
||
var sample = toArray(obj);
|
||
var length = _getLength(sample);
|
||
n = Math.max(Math.min(n, length), 0);
|
||
var last = length - 1;
|
||
for (var index = 0; index < n; index++) {
|
||
var rand = random(index, last);
|
||
var temp = sample[index];
|
||
sample[index] = sample[rand];
|
||
sample[rand] = temp;
|
||
}
|
||
return sample.slice(0, n);
|
||
}
|
||
|
||
module.exports = sample;
|