Coroutine runner

coroutinerunner.js

function* waitSeconds(duration) {
  while (duration > 0) {
    duration -= globals.deltaTime;
    yield;
  }
}

function* waitFrames(numFrames) {
  while (numFrames > 0) {
    --numFrames;
    yield;
  }
}

class CoRoutineRunner {
  constructor() {
    this.generatorStacks = [];
    this.addQueue = [];
    this.removeQueue = new Set();
  }
  get isBusy() {
    return this.addQueue.length + this.generatorStacks.length > 0;
  }
  add(generator, delay = 0) {
    const genStack = [generator];
    if (delay) {
      genStack.push(waitSeconds(delay));
    }
    this.addQueue.push(genStack);
  }
  remove(generator) {
    this.removeQueue.add(generator);
  }
  update() {
    this._addQueued();
    this._removeQueued();
    for (const genStack of this.generatorStacks) {
      const main = genStack[0];
      // Handle if one coroutine removes another
      if (this.removeQueue.has(main)) {
        continue;
      }
      while (genStack.length) {
        const topGen = genStack[genStack.length - 1];
        const {value, done} = topGen.next();
        if (done) {
          if (genStack.length === 1) {
            this.removeQueue.add(topGen);
            break;
          }
          genStack.pop();
        } else if (value) {
          genStack.push(value);
        } else {
          break;
        }
      }
    }
    this._removeQueued();
  }
  _addQueued() {
    if (this.addQueue.length) {
      this.generatorStacks.splice(this.generatorStacks.length, 0, ...this.addQueue);
      this.addQueue = [];
    }
  }
  _removeQueued() {
    if (this.removeQueue.size) {
      this.generatorStacks = this.generatorStacks.filter(genStack => !this.removeQueue.has(genStack[0]));
      this.removeQueue.clear();
    }
  }
}

test.js

function* test02() {
  console.log('Go');
  yield;
  console.log('Gogo');
  yield waitFrames(3);
  console.log('Gogo2');
  yield waitFrames(3);
}

function* test01() {
  console.log('hello');
  yield;
  console.log('world');
  yield test02();
  console.log('!');
}

console.log('start');
const runner = new CoRoutineRunner();
runner.add(test01());

let count = 0;
while (runner.isBusy) {
  console.log('---------:', count++);
  runner.update();

  if (count > 50) {
    break;
  }
}
console.log('end');