var fib = [0, 1];
for (var i = 2; i < n; i++) {
    fib[ i ] = fib[ i - 1 ] + fib[ i - 2 ];
    console.log(fib);
}

fib[ 3 ] = fib[ 3 - 1 ] + fib[ 3 - 2 ];
fib[ 3 ] = fib[ 2 ] + fib[ 1 ];
fib[ 3 ] = fib[ 3 ];

var fib = [0,1,1,3]

fib[ 3 ] = fib[ 3 - 1 ] + fib[ 3 - 2 ];
fib[ 3 ] = fib[ 2 ] + fib[ 1 ];
fib[ 3 ] = fib[ 3 ];

fib[ 3 ] = fib[ 3 - 1 ] + fib[ 3 - 2 ];
fib[ 3 ] = fib[ 2 ] + fib[ 1 ];
fib[ 3 ] = 1 + 1;

[0,1,1,2]

fib[0] = 0
fib[1] = 1
fib[2] = 1
fib[3] will equal 2

fib[4] = fib[4-1] +fib[4-2]
fib[4] = fib[3] + fib[2]
fib[4] = 1 + 2
fib[4] = 3

var fib = [0, 1];
for (var i = 2; i < 10; i++) {
    fib[ i ] = fib[ i - 1 ] + fib[ i - 2 ];
    console.log(fib);
}

fib[ 3 ] = fib[ 3 - 1 ] + fib[ 3 - 2 ];
fib[ 3 ] = fib[ 2 ] + fib[ 1 ];
fib[ 3 ] = fib[ 3 ];

fib[3] = fib[2] + fib[1]
fib[3] = fib[3]