查找字符串中最大连续字符

/* 最大连续字符 */
(function(str){
    str = str || '';
    var startIndex = max_char_start = 0,
        offset = max_char_offset = 1;
    for(var i = 1, len = str.length; i < len; i++){
        var current_char = str[i];
        var prev_char = str[i - 1];
        if(current_char == prev_char){
            offset = offset + 1;
            // 如果存在最大连续字符相同的情况，可以判断是显示第一个，还是最后一个
            if((i + 1 < len) && (current_char != str[i + 1]) && offset > max_char_offset){
                max_char_start = startIndex;
                max_char_offset = offset;
            }
        }
        else{
            startIndex = i;
            offset = 1;
        }
    }
    console.log(str.substr(max_char_start, max_char_offset) + ' from ' + max_char_start + ' offset: ' + max_char_offset);
})("aabbcccdddddeeeeeeeeeeefffffff")