Moving average

movingave.js

//Moving average
// v(t) = a * V(t) + (1-a)*v(t-1)

// http://scrollerjs.com/talks/velocity2014/#1

function moveStep () { // triggered every 17ms~
    var v = (currentPos - prevPos) / (currentTime - prevTime); // current velocity
    self.velocity = 0.6 * v + 0.4 * self.velocity; // Applying moving average formmula
    self.translate(self.x, self.y); // debounce move event from animation
    requestAnimationFrame(moveStep);
}

// http://ariya.ofilabs.com/2013/11/javascript-kinetic-scrolling-part-2.html

// scroll to a given position in a give time (momentum)
scrollTo: function (pos, duration, curve) {
    var startTime = NOW(),
        deltaPos    = startPos - pos,
        destTime    = startTime + duration;
 
    function step () {
      var now = NOW();
      if (now >= destTime) { 
          return; // Animation is done!
      }
      percentageTime     = (now - startTime) / duration;
      percentageProgress = curve(percentageTime); 
 
      // Calculate new position based on the result of the function
      newPos = deltaPos * percentageProgress + startPos;
 
      requestAnimationFrame(step);
    }
    step();
}


// scroller
attachItemInSurface: function (item, surface, config) {
    var offset = config.offset;

    // Recalculate styles (DOM write)
    surface.dom.appendChild(item.dom);

    // This will force a paint (DOM read)
    height = surface.dom.offsetHeight;

    offsetY = offset - height;
    surface.dom.style[transform] = 
        'translate3d(0, ' + offsetY + ', 0)';
}

//plugins
var myPlugin = {
    init: function () {
        this.on('_update', this._updateMyPlugin);   // Register a listener on update
        this.on('_refresh', this._refreshMyPlugin); // Register a listener on refresh
    },
    _getVelocity: function () { // Overrides the original scroller function
      return 2;
    },
    _refreshMyPlugin: function () { // Adds some internal state
      this.state = 'refreshed';
    },
    _updateMyPlugin: function () { // Do something external to the scroller
        var str = this.opts.myPlugin;
        console.log(str + this.y);
    }
};

//Attach plugins to the scroller
var scroller = new Scroller('#wrapper', {myPlugin: 'YAY!: '});
scroller.plug(myPlugin);

//Add and initialize plugins on bootstrap
var scroller2 = new Scroller('#wrapper', {
    plugins: ['MyPlugin2'] // If is already registered under Scroller.plugins
});