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switch to exponent operator

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atomiks
2017-12-31 19:04:35 +11:00
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snippets/elo.md
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@ -4,13 +4,13 @@ Computes the new ratings between two opponents using the [Elo rating system](htt
of two pre-ratings and returns an array containing two post-ratings.
The winner's rating is the first element of the array.
Use `Math.pow()` and math operators to compute the expected score (chance of winning) of each opponent
and compute the new rating for each. Omit the second argument to use the default K-factor of
32, or supply a custom K-factor value.
Use the exponent `**` operator and math operators to compute the expected score (chance of winning)
of each opponent and compute the new rating for each. Omit the second argument to use the default
K-factor of 32, or supply a custom K-factor value.
```js
const elo = ([a, b], kFactor = 32) => {
const expectedScore = (self, opponent) => 1 / (1 + Math.pow(10, (opponent - self) / 400));
const expectedScore = (self, opponent) => 1 / (1 + 10 ** ((opponent - self) / 400));
const newRating = (rating, i) => rating + kFactor * (i - expectedScore(i ? a : b, i ? b : a));
return [newRating(a, 1), newRating(b, 0)];
};