| 1 | export function extremaBy(source, selector, comparer) {
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| 2 | let result = [];
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| 3 | const it = source[Symbol.iterator]();
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| 4 | const { value, done } = it.next();
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| 5 | if (done) {
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| 6 | throw new Error('Sequence contains no elements');
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| 7 | }
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| 8 | let resKey = selector(value);
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| 9 | result.push(value);
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| 10 | let next;
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| 11 | while (!(next = it.next()).done) {
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| 12 | const current = next.value;
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| 13 | const key = selector(current);
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| 14 | const cmp = comparer(key, resKey);
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| 15 | if (cmp === 0) {
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| 16 | result.push(current);
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| 17 | }
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| 18 | else if (cmp > 0) {
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| 19 | result = [current];
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| 20 | resKey = key;
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| 21 | }
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| 22 | }
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| 23 | return result;
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| 24 | }
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| 25 |
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| 26 |
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