//For loop
function sumToN(n)
{
    var sum = 0;
    for(var i = n; i > 0; i--)  //Could also be written as for(var i = 1; i <= n; i++)
    {
        sum = sum + i;  //Can also be written sum += i
    }
    return sum;
}

//Recursive
function sumToN(n)
{
    if(n > 0)
    {
        return n + sumToN(n - 1);
    }
    else
    {
        return 0;
    }
}

//While loop
function sumToN(n)
{
    var sum = 0;
    while(n > 0)
    {
        sum = sum + n;
        n--;  //Can also be written n = n - 1, or n -= 1
    }
    return sum;
}