runTaskWhileValid.js

Cu.import("resource://gre/modules/Task.jsm")

let runTaskWhileValid = (isValid, generator) => {
  Task.spawn(function* () {
    const g = generator();
    let value, resolved;
    let done = false;
    while (!done) {
      try {
        ({ value, done }) = g.next(resolved);
        resolved = yield value;
      } catch (e) {
        g.throw(e);
      }

      if (!isValid()) {
        done = true;
        resolved = undefined;
        console.log(done)
      }
    }
    return resolved;
  });
};

let getRandomIn10ms = () => new Promise(resolve => setTimeout(() => resolve(Math.random()), 10));


let start = Date.now();
let lessThan50ms = () => Date.now() - start < 50;

runTaskWhileValid(lessThan50ms, function* () {
  let i = 0;
  while (true) {
    console.log("iteration number ", i++);
    let rand = yield getRandomIn10ms();
    console.log("rand = ", rand);
  }
});