---
type: snippet
tags: ['parallel', 'serial']
status: release
ctime: 2025-03-05
mtime: 2025-03-05
---

import QuoteLink from '@components/QuoteLink.astro'

<QuoteLink url="https://stackblitz.com/edit/vitest-dev-vitest-jtqzu5sy?file=test%2Fbasic.test.ts">
  TaskRunner Test
</QuoteLink>

```ts
type Task = (callback: (result: string) => void) => void

type TasksCallback = (results: string[]) => void

class TaskRunner {
  protected tasks: Task[] = []

  protected results: Array<string> = []

  addTask(task: Task) {
    this.tasks.push(task)
  }
}

class ParallelTaskRunner extends TaskRunner {
  run(callback: TasksCallback) {
    const totalTasks = this.tasks.length

    this.tasks.forEach((task) => {
      task((result) => {
        this.results.push(result)

        if (this.results.size === totalTasks) {
          callback([...this.results])
        }
      })
    })
  }
}

class SerialTaskRunner extends TaskRunner {
  index = 0

  run(callback: TasksCallback) {
    const executeTask = () => {
      if (this.index >= this.tasks.length) {
        callback([...this.results])
        return
      }

      this.tasks[this.index]((result) => {
        this.results.push(result)

        this.index++

        executeTask()
      })
    }

    executeTask()
  }
}
```

- [Node.js script to run multiple commands in parallel · Muffin Man](https://muffinman.io/blog/node-script-to-run-multiple-commands-in-parallel/)[^485-1]

---

[^485-1]: [concurrently](https://github.com/open-cli-tools/concurrently)