const scope = () => {
        if (point === 'top') {
            return elemTop;
        }
        else if (point === 'middle') {
            return elemTop + (elemHeight/2);
        }
        else if (point === 'bottom') {
            return elemTop + elemHeight;
        }
        else if (typeof point === 'Number') {
            return elemTop + point;
        }
        else if (typeof point === 'String')
            var value = point.match(/\d+/)[0];
            // value is a percentage
            if (point.indexOf('%') >= 0) {
                return elemTop + (elemHeight/100 * value)
            }
            // value is in pixels
            else if (point.indexOf('px') >= 0) {
                return elemTop + value;
            }
        else {
            return console.warn('inViewport: you must pass a valid value for "scope"')
        }
    }