Javascript Algorithm:Fibonacci Sequence

Fibonacci Sequence:

The Fibonacci sequence is a sequence in which each number is the sum of the

two preceding ones. Numbers that are part of the Fibonacci sequence are known

as Fibonacci numbers, commonly denoted Fn .

The sequence commonly starts from 0 and 1.the sequence is as below

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144,..

How to generate fibonanci Sequence in Javascript:

Each function below prints all fibonancci numbers less than 10.

Solution 1:

function fibonacciSequence(max) {

let startPoint = 0;

let current = 1;

let arr = [0, 1];

let next = startPoint + current;

while (next < max) {

arr.push(next);

startPoint = current;

current = next;

next = startPoint + current;

}

return arr;

}

var resultArray = fibonacciSequence(10);

console.log(resultArray);

Output:

[

0, 1, 1, 2,

3, 5, 8

]

Solution 2:

function fibonacciSequence(max) {

let startPoint = 0;

let current = 1;

console.log(startPoint)

console.log(current)

let next = startPoint + current;

while (next < max) {

console.log(next)

startPoint = current;

current = next;

next = startPoint + current;

}

}

fibonacciSequence(10);

Output:

0

1

1

2

3

5

8

Solution2: Using generator function.

function* fibonacciSequenceGenerator(max) {

let startPoint = 0;

let current = 1;

yield startPoint

yield current

let next = startPoint + current;

while (next < max) {

yield next

startPoint = current;

current = next;

next = startPoint + current;

}

}

let iterator = fibonacciSequenceGenerator(10)

for(let val of iterator){

console.log(val)

}

Output:

0

1

1

2

3

5

8

Solution3:Using Recursion.

function fibonacciSequenceRecursive(index) {

switch (index) {

case 0:

return 0;

case 1:

case 2:

return 1;

default:

return (

fibonacciSequenceRecursive(index - 1) +

fibonacciSequenceRecursive(index - 2)

);

}

}

for (let i = 0; fibonacciSequenceRecursive(i) < 10; i++) {

let si = fibonacciSequenceRecursive(i);

console.log(si);

}

Output:

0

1

1

2

3

5

8

Solution 4: Using generator function

function* fibonacciSequenceGenerator(max) {

let result = 0;

let index = 1;

let obj = {};

while (result < max) {

yield result;

if (index == 1 || index == 2) {

result = 1;

obj[index] = result;

} else {

result = obj[index - 1] + obj[index - 2];

obj[index] = result;

}

index++;

}

}

let iterator = fibonacciSequenceGenerator(10);

for (let val of iterator) {

console.log(val);

}

Output:

0

1

1

2

3

5

8

Solution 5: Using two generator functions:

function* fibonacciGenerator() {

let prev = 0;

let curr = 1;

while (true) {

yield curr;

[prev, curr] = [curr, prev + curr];

}

}

function* firstNFibonacci(max) {

const fibonacci = fibonacciGenerator();

let result = fibonacci.next().value;

while (result < max) {

yield result;

result = fibonacci.next().value;

}

}

// Create a generator instance for the first 3 Fibonacci numbers

const iterator = firstNFibonacci(10);

// Generate and print the first 3 Fibonacci numbers

for (const val of iterator) {

console.log(val);

}

Output:

0

1

1

2

3

5

8