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JavaScript - Fibonacci sequence / number

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Created by:

chelsea

806

Fibonacci numbers can be computed in three ways:

with an iterative algorithm,
with a recursive algorithm,
with Binet's formula.

Note: presented implementations calculate Fibonacci numbers from 0.

1. Iterative algorithm example

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function calculateValue(number) {
    if(number < 1) {
        return 0;
    }
    var a = 0;
    var b = 1;
    for (var i = 1; i < number; ++i) {
        var c = a + b;
        a = b;
        b = c;
    }
    return b;
}
​
​
// Usage example:
​
for (var n = 0; n < 10; ++n) {
    var value = calculateValue(n);
    console.log('f(' + n + ')=' + value);
}

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2. Recursive algorithm example

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function calculateValue(number) {
    if(number < 1) return 0;
    if(number < 2) return 1;
    return calculateValue(number - 2) + calculateValue(number - 1);
}
​
​
// Usage example:
​
for (var n = 0; n < 10; ++n) {
    var value = calculateValue(n);
    console.log('f(' + n + ')=' + value);
}

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3. Binet's formula example

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function calculateValue(number) {
    var a = Math.pow(1 + 2.23606797749979, number);
    var b = Math.pow(1 - 2.23606797749979, number);
    var c = 2.23606797749979 * Math.pow(2, number);
    return Math.round((a - b) / c);
}
​
​
// Usage example:
​
for (var n = 0; n < 10; ++n) {
    var value = calculateValue(n);
    console.log('f(' + n + ')=' + value);
}