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| function extractRandomSubset (fullSet, subsetLength) { | |
| var maxIndex, i, m, selectedItemIndex, selectedItem; | |
| if(!fullSet.length){ | |
| return []; | |
| } | |
| maxIndex = fullSet.length - 1; | |
| for (i = maxIndex, m = 0; i >= 0 && m < subsetLength; i--, m++) { | |
| // find item between start of the set and | |
| // ever decreasing index, which starts at the end of the set | |
| selectedItemIndex = Math.round(Math.random() * i); | |
| selectedItem = fullSet[selectedItemIndex]; | |
| // put found item to the end of the set | |
| fullSet[selectedItemIndex] = fullSet[i]; | |
| fullSet[i] = selectedItem; | |
| } | |
| // extract (and remove) the end of the set, | |
| // populated with found random items | |
| return fullSet.splice(fullSet.length - m, m); | |
| } |
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