Kinetic scrolling with Greasemonkey by binauralbeat

Original thread

// ==UserScript==
// @name Kinetic
// @namespace 
// @include *
// @description 
// ==/UserScript==

var TIME_THRESHOLD = 500;
var MAX_VELOCITY = 5000;

var scrollBy;
var sintv;
var startY = 0;
var endY = 0;
var startTime;
var endTime;
var timeScrolled;
var distanceScrolled;
var velocity;
var direction;


var intervalCount = 0;

function setStartY(e){
        stopScroll();
        startY = e.pageY;
        startTime = new Date();
}

function startScroll(e){
        stopScroll();
        endY = e.pageY;
        endTime = new Date();
        if(e.pageX < 700){  // 700 should be innerwidth of window ... change me
                Scroll(startY, endY, startTime, endTime);
        }
}


function Scroll(stY,enY,stTime,enTime){

        timeScrolled = (enTime.getSeconds()+ enTime.getMilliseconds()/1000) - 

(stTime.getSeconds()+stTime.getMilliseconds()/1000);

        

        if(timeScrolled < TIME_THRESHOLD){

                distanceScrolled = Math.abs(enY - stY);

                velocity = (distanceScrolled / timeScrolled);

                if(velocity > MAX_VELOCITY){
                        velocity = MAX_VELOCITY;
                }

                
                //get direction
                if(enY > stY){
                        direction = -1;
                }else{
                        direction = 1;
                }

                sintv = setInterval(scrollIt, 10);
                
        }
}

function scrollIt(){

        intervalCount +=1;

        var cseconds = 1+intervalCount/100;

        scrollBy = (velocity*0.098)/(cseconds*cseconds);

        if(scrollBy > 2){
                window.scrollBy(0,parseInt(scrollBy * direction));
        }else{
                stopScroll();
        }
        
}

function stopScroll(){
        
        direction = 0;
        velocity = 0;
        intervalCount = 0;
        distanceToScroll = 0;
        clearInterval(sintv);
}