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30-seconds-of-code/snippets_archive/fibonacciUntilNum.md
Angelos Chalaris 0425ebefe7 Archive, multitagging, cleanup
Cleaned up the current snippets for consistency and minor problems, added multiple tags to most of them, archived a few.
2018-01-05 16:33:54 +02:00

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### fibonacciUntilNum
Generates an array, containing the Fibonacci sequence, up until the nth term.
Create an empty array of the specific length, initializing the first two values (`0` and `1`).
Use `Array.reduce()` to add values into the array, using the sum of the last two values, except for the first two.
Uses a mathematical formula to calculate the length of the array required.
```js
const fibonacciUntilNum = num => {
let n = Math.ceil(Math.log(num * Math.sqrt(5) + 1 / 2) / Math.log((Math.sqrt(5) + 1) / 2));
return Array.from({ length: n }).reduce(
(acc, val, i) => acc.concat(i > 1 ? acc[i - 1] + acc[i - 2] : i),
[]
);
};
```
```js
fibonacciUntilNum(10); // [ 0, 1, 1, 2, 3, 5, 8 ]
```