Javascript Interview Question Number get n-th Fibonacci Number

Introduction

Fibonacci Sequence is characterized by the fact that every number after the first two is the sum of the two preceding ones

Except the first two numbers in the sequence

The Fibonacci Sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144 ...

Given input number n, return the nth fibonacci number in the sequence 

nthFibonacci(5) should return 3
nthFibonacci(22) should return 10946

Test cases: 



function nthFibonacci(n) {

}
/*  Do not edit below this line */

var line = '****************************************************************';
var passed = 0;/*from   w  w w.  j av  a  2 s .  co m*/
var failed = 0;

console.log(line);
console.log('nthFibonacci UNIT TESTS');
console.log(line);

if (nthFibonacci(5) === 3) {
    console.log("Test 1 pass, nthFibonacci(5) returns 3");
    passed += 1;
} else {
    console.log("Test 1 failed, nthFibonacci(5) should return 3");
    failed += 1;
}

if (nthFibonacci(22) === 10946) {
    console.log("Test 2 pass, nthFibonacci(22) returns 10946");
    passed += 1;
} else {
    console.log("Test 2 failed, nthFibonacci(22) should return 10946");
    failed += 1;
}

if (nthFibonacci(1) === 0) {
    console.log("Test 3 pass, nthFibonacci(1) returns 0");
    passed += 1;
} else {
    console.log("Test 3 failed, nthFibonacci(1) should return 0");
    failed += 1;
}

console.log(line);
console.log('TOTAL TESTS PASSED: ' + passed );
console.log('TOTAL TESTS FAILED: ' + failed );
console.log(line);




// A helper function that returns the next number in the fibonacci sequence given the current fibonacci sequence
function nextFib(fibonacciSequence) {
    var sequenceLength = fibonacciSequence.length;

    return fibonacciSequence[sequenceLength - 1] + fibonacciSequence[sequenceLength - 2];
}

function nthFibonacci(n) {
    // Initialize our sequence so we have at minimal numbers needed to calculate the next number in sequence
    var fibonacciSequence = [0, 1];

    // Continue to add more numbers to our sequence until we have at least n number of numbers in our sequence 
    while (fibonacciSequence.length < n) {
        fibonacciSequence.push(nextFib(fibonacciSequence));
    }

    return fibonacciSequence[n - 1];
}

/*  Do not edit below this line */

var line = '****************************************************************';
var passed = 0;
var failed = 0;

console.log(line);
console.log('nthFibonacci UNIT TESTS');
console.log(line);

if (nthFibonacci(5) === 3) {
    console.log("Test 1 pass, nthFibonacci(5) returns 3");
    passed += 1;
} else {
    console.log("Test 1 failed, nthFibonacci(5) should return 3");
    failed += 1;
}

if (nthFibonacci(22) === 10946) {
    console.log("Test 2 pass, nthFibonacci(22) returns 10946");
    passed += 1;
} else {
    console.log("Test 2 failed, nthFibonacci(22) should return 10946");
    failed += 1;
}

if (nthFibonacci(1) === 0) {
    console.log("Test 3 pass, nthFibonacci(1) returns 0");
    passed += 1;
} else {
    console.log("Test 3 failed, nthFibonacci(1) should return 0");
    failed += 1;
}

console.log(line);
console.log('TOTAL TESTS PASSED: ' + passed );
console.log('TOTAL TESTS FAILED: ' + failed );
console.log(line);



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