var first = 0; // initialise first number
var second = 1; // initialise second number
var temp = NaN; // a temporary variable for swapping
// calculate the third fibinacci number
temp = second; 
second = first + second;
first = temp;
// calculate the fourth fibinacci number
temp = second; 
second = first + second;
first = temp;
// calculate the fifth fibinacci number
temp = second; 
second = first + second;
first = temp;
console.log(`first: ${first}, second:${second}`);