find the max 0's in-between 1's in a binary number

Binary Gap

function solution(N) {
    var maxGap = 0;
    var tempGap = 0;
    var count = 0;
    
    var binGap = N.toString(2);
    var lastIndex = binGap.length - 1;
    
    for (lastIndex; lastIndex>=0; lastIndex--) {
        if (binGap[lastIndex] !== '0') {
            break;
        }
    }
    
    for (var i=lastIndex-1; i>=0; i--) {
        if (binGap[i] === '0') {
            count += 1
            tempGap = count
        } else {
            if (tempGap > maxGap) {
                maxGap = tempGap
            }
            count = 0
        }
    }
    return maxGap
}