worst case to find max in array:
function max(array) {
    for (const itemA of array) {
        // Assume that it is the maximum value until we know otherwise
        let isMax = true;

        for (const itemB of array) {
            if (itemA < itemB) {
                // There is a value greater than itemA, so it is not the
                // maximum
                isMax = false;
            }
        }

        if (isMax) {
            return itemA;
        }
    }
};

next worst-

function max(array) {
    for (const itemA of array) {
        // Assume that it is the maximum value until we know otherwise
        let isMax = true;

        for (const itemB of array) {
            if (itemA < itemB) {
                // There is a value greater than itemA, so it is not the
                // maximum
                isMax = false;
                // Don't keep checking the value
                break;
            }
        }

        if (isMax) {
            return itemA;
        }
    }
};
BEST CASE -

function max(array) {
    if (array.length === 0) {
        return null;
    }

    let currentMax = array[0];
    for (let i=1; i<array.length; i++) {
        const item = array[i];
        if (item > currentMax) {
            currentMax = item;
        }
    }
    return currentMax;
};