Which of these is a better procedure for calculating the max value in a Javascript array?

Procedure 1:

function getMax ( arr ) 
{
    // returns the maximum value in the array arr
    // returns undefined if array is empty
    var max = Number.MIN_VALUE;
    for (var i = 0, j = arr.length; i < j; ++i)
    {
        thisval = arr[i];
        if (thisval > max) max = thisval;
    }
    return max;
}

Procedure 2:

function getMax ( arr ) 
{
    // returns the maximum value in the array arr
    // returns undefined if array is empty
    var j = arr.length;
    if (j == 0) return undefined;
    var max = arr[0];
    for (var i = 1; i < j; ++i)
    {
        thisval = arr[i];
        if (thisval > max) max = thisval;
    }
    return max;
}

I'm wondering which would be considered better in terms of efficiency, compactness, readability, cleverness, maintainability, handling corner cases, etc. In other words, which one of those would I used if I was in a coding interview?