Method scheduleTimer

packages/core/src/defer/timer_scheduler.ts:123–209

(ngZone: NgZone)

  }

  private scheduleTimer(ngZone: NgZone) {
    const callback = () => {
      this.clearTimeout();

      this.executingCallbacks = true;

      // Clone the current state of the queue, since it might be altered
      // as we invoke callbacks.
      const current = [...this.current];

      // Invoke callbacks that were scheduled to run before the current time.
      const now = Date.now();
      for (let i = 0; i < current.length; i += 2) {
        const invokeAt = current[i] as number;
        const callback = current[i + 1] as VoidFunction;
        if (invokeAt <= now) {
          callback();
        } else {
          // We've reached a timer that should not be invoked yet.
          break;
        }
      }
      // The state of the queue might've changed after callbacks invocation,
      // run the cleanup logic based on the *current* state of the queue.
      let lastCallbackIndex = -1;
      for (let i = 0; i < this.current.length; i += 2) {
        const invokeAt = this.current[i] as number;
        if (invokeAt <= now) {
          // Add +1 to account for a callback function that
          // goes after the timestamp in events array.
          lastCallbackIndex = i + 1;
        } else {
          // We've reached a timer that should not be invoked yet.
          break;
        }
      }
      if (lastCallbackIndex >= 0) {
        arraySplice(this.current, 0, lastCallbackIndex + 1);
      }

      this.executingCallbacks = false;

      // If there are any callbacks added during an invocation
      // of the current ones - move them over to the "current"
      // queue.
      if (this.deferred.length > 0) {
        for (let i = 0; i < this.deferred.length; i += 2) {
          const invokeAt = this.deferred[i] as number;
          const callback = this.deferred[i + 1] as VoidFunction;
          this.addToQueue(this.current, invokeAt, callback);
        }
        this.deferred.length = 0;
      }
      this.scheduleTimer(ngZone);
    };

    // Avoid running timer callbacks more than once per
    // average frame duration. This is needed for better