innerHTML speed test code

prove.js

var bodyHtml = document.body.innerHTML;
function a() {
  var date = Date.now();
  document.body.innerHTML = Math.random().toString() + 'test';
  console.log('render ' + (Date.now() - date) + 'ms');
  setTimeout(a, 0);
}
function b() {
  var date = Date.now();
  document.body.innerHTML = bodyHtml;
  console.log('render ' + (Date.now() - date) + 'ms');
  setTimeout(b, 0);
}
a();
b();