Fibonacci sequence in Rust and JavaScript

fib.js

function fib(nth) {
  const vec = [0, 1];
  let i = 2;

  while (i <= nth) {
    const val = vec[0] + vec[1];

    vec[0] = vec[1];
    vec[1] = val;

    i += 1;
  }

  return vec[1];
}

function fibSeq(nth) {
  const vec = [0, 1, 1];
  let i = 3;

  while (i <= nth) {
    vec.push(vec[i - 1] + vec[i - 2]);

    i += 1;
  }

  return vec;
}

function main() {
  console.log(`20th term: ${fib(20)}`);
  console.log(`Fibonacci sequence: [${fibSeq(20).join()}]`);
}

main();

fib.rs

fn fib(nth: i32) -> u32  {
    let mut vec = (0, 1);

    for _ in 2..=nth {
        let val = vec.0 + vec.1;
        vec = (vec.1, val);
    }

    vec.1
}

fn fib_seq(nth: usize) -> Vec<i32> {
    let mut vec = vec![0, 1, 1];

    for n in 3..=nth {
        vec.push(vec[n - 1] + vec[n - 2]);
    }

    vec
}

fn main() {
    println!("20th term: {}", fib(20));
    println!("Fibonacci sequence: {:?}", fib_seq(20));
}