Generating Fibonacci Sequence

var x = 0;
var y = 1;
var z;

fib[0] = 0;
fib[1] = 1;

for (i = 2; i <= 10; i++) {
  alert(x + y);
  fib[i] = x + y;
  x = y;
  z = y;
}

I'm trying to get to generate a simple Fibonacci Sequence but there no output.

Can anybody let me know what's wrong?

You have never declared fib to be an array. Use var fib = []; to solve this.

Also, you're never modifying the y variable, neither using it.

The code below makes more sense, plus, it doesn't create unused variables:

var i;
var fib = []; // Initialize array!

fib[0] = 0;
fib[1] = 1;
for (i = 2; i <= 10; i++) {
  // Next fibonacci number = previous + one before previous
  // Translated to JavaScript:
  fib[i] = fib[i - 2] + fib[i - 1];
  console.log(fib[i]);
}

According to the Interview Cake question, the sequence goes 0,1,1,2,3,5,8,13,21. If this is the case, this solution works and is recursive without the use of arrays.

function fibonacci(n) {
   return n < 1 ? 0
        : n <= 2 ? 1
        : fibonacci(n - 1) + fibonacci(n - 2)
}

console.log(fibonacci(4))

Think of it like this.

   fibonacci(4)   .--------> 2 + 1 = 3
      |          /               |
      '--> fibonacci(3) + fibonacci(2)
            |    ^           
            |    '----------- 2 = 1 + 1 <----------.
1st step -> |                     ^                |
            |                     |                |
            '---->  fibonacci(2) -' + fibonacci(1)-'

Take note, this solution is not very efficient though.