It is similar in spirit to java.io.Closeable, but without the I/O focus, or to IDisposable in Microsoft .NET.

// Scheduling execution with a 10 seconds delay
const ref = setTimeout(() => console.log("Hello1"), 10000)
const task = Cancelable.of(() => clearTimeout(ref))

// If we change our mind
task.cancel()

In case some API requires the return of an ICancelable reference, but there isn't anything that can be canceled, then Cancelable.empty can be used to return a reusable reference that doesn't do anything when canceled.

const task = Cancelable.empty()

// It's a no-op, doesn't do anything
task.cancel()

Implementation sample:

class MyCancelable implements ICancelable {
  // Idempotency guard
  private _isCanceled: boolean = false

  cancel() {
    // We need an idempotency guarantee, any side-effects
    // need to happen only once
    if (!this._isCanceled) {
      this._isCanceled = true
      console.log("Was canceled!")
    }
  }
}