Fibonacci Number

LeetCode題目: 509. Fibonacci Number

My solution:

/**
 * @param {number} n
 * @return {number}
 */
let fib = n => {
    if(n === 1 || n === 0) return n;
    let prev1 = 0, prev2 = 1, curr;
    for(let i=2; i<=n; i++) {
        curr = prev2 + prev1;
        prev1 = prev2;
        prev2 = curr;
    }
    return curr;
}