JS Code

function fibonacciJS(num) {
  if (num == 1) return 0;
  if (num == 2) return 1;
  let num1 = 0;
  let num2 = 1;
  let i = 2;
  while (i < num) {
    const sum = num1 + num2;
    num1 = num2;
    num2 = sum;
    i += 1;
  }
  return num2;
}
        

Rust Code

pub fn fibonacci(n: i64) -> i64 {
  if n == 0 {
      return 0;
  } else if n == 1 {
      return 1;
  } else {
      let mut a = 0;
      let mut b = 1;
      for _i in 2..n {
          let c = a + b;
          a = b;
          b = c;
      }
      return b;
  }
}