canvas = document.getElementById( 'canvas' );
context = canvas.getContext( '2d' );

var x = 0;
var coords = new Array();

function draw() {
  canvas.width = canvas.width;

  context.moveTo(0, 80);

  x+=10;

  if(x>300){
    for(var i in coords){
      coords[i].x=coords[i].x-10;
    }	
  }

  var temp = {
    x : x,
      y : Math.floor(Math.random()*80)+40
  };

  coords.push(temp);

  for(var i in coords){
    context.lineTo(coords[i].x, coords[i].y);
  }

  context.strokeStyle="#9fdcf3";
  context.lineWidth = 1;
  context.shadowColor = '#9fdcf3';
  context.shadowBlur = 10;

  context.stroke();
  context.closePath();

}

setInterval(draw,100);