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