Most efficient way to calculate Fibonacci sequence in Javascript

I'm attempting to get better with optimizing algorithms and understanding big-o, etc.

I threw together the below function to calculate the n-th Fibonacci number. This works (for a reasonably high input). My question is, how can I improve this function? What are the drawbacks of calculating the Fibonacci sequence this way?

function fibo(n) {  

    var i;
    var resultsArray = [];  

    for (i = 0; i <= n; i++) {
        if (i === 0) {
            resultsArray.push(0);
        } else if (i === 1) {
            resultsArray.push(1);
        } else {
            resultsArray.push(resultsArray[i - 2] + resultsArray[i - 1]);
        }
    }

    return resultsArray[n];
}

I believe my big-o for time is O(n), but my big-o for space is O(n^2) due to the array I created. Is this correct?

---

如果您没有阵列，则可以节省内存和.push调用

function fib(n) {
    var a = 0, b = 1, c;
    if (n < 3) {
        if (n < 0) return fib(-n);
        if (n === 0) return 0;
        return 1;
    }
    while (--n)
        c = a + b, a = b, b = c;
    return c;
}

---

表现斐波纳契：

    var memo = {};
    var countInteration = 0;
    var fib = function (n) {
        if (memo.hasOwnProperty(n)) {
            return memo[n];
        }
        countInteration++;
        console.log("Interation = " + n);
        if (n == 1 || n == 2) {
            result = 1;
        } else {
            result = fib(n - 1) + fib(n - 2);
        }
        memo[n] = result;
        return result;
    }
    //output `countInteration` = parameter `n`

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