index.js

var raf = require("raf");

raf(function loop (t) {
  raf(loop);
  if (isVisibleInWindow(canvas)) return;
  // ... do your consuming stuff
});

use-case.js

var raf = require("raf");

var lastFrame;
raf(function loop (t) {
  raf(loop);
  if (isVisibleInWindow(canvas)) {
    lastFrame = t;
    return;
  }
  if (!lastFrame) lastFrame = t;
  var dt = t - lastFrame;
  lastFrame = t;
  // ... do your consuming stuff
  // dt is the delta time with the last frame
});