//main class
function Section(){
    this.current;
}

//constructor
Section.prototype.construct = function(topOffset,offsets) {

    for (var i = 0; i < offsets.length; i++) {
        if (topOffset >= offsets[i] && topOffset < offsets[i + 1]) {
            this.current = offset[i];
        }
    }
}

//get current
Section.prototype.getCurrent = function() {
    return this.current;
}

var Section = new Section();
Section.construct(topOffset,offsets);