var icon = require('favicon');
var canvas = document.createElement('canvas');
canvas.width = canvas.height = 16;
var ctx = canvas.getContext('2d');
ctx.font = '16px Helvetica, Arial, sans-serif';
var nums = [0,1,2,3,4,5,6,7,8,9];
var i = 0;
setInterval(function(){
  ctx.clearRect(0, 0, 16, 16);
  var n = nums[i++ % 10];
  ctx.fillText(n, 0, 15);
  icon(canvas.toDataURL());
}, 300);