Refactor from Frontend to Backend

To improve performance, let’s refactor the frontend code and move it to the backend.

Step 1: Create the Backend Method

We’ll add a shared/TasksController.ts file with the following code:

import { BackendMethod, remult } from 'remult'
import { Task } from './Task.js'

export class TasksController {
  @BackendMethod({ allowed: true })
  static async setAllCompleted(completed: boolean) {
    const taskRepo = remult.repo(Task)
    for (const task of await taskRepo.find()) {
      await taskRepo.update(task, { completed })
    }
  }
}

Code Explanation

• We created a TasksController class to contain backend methods.
• The setAllCompleted method is decorated with @BackendMethod({ allowed: true }), making it accessible from the frontend.
• Inside setAllCompleted, we get the repository for Task using remult.repo(Task).
• We iterate through the tasks and update each one with the new completed status.
• Previously, in the frontend, the taskRepo repository performed HTTP calls to the backend. Now that we’re on the backend, the taskRepo repository makes direct API calls to the database.
• An advantage of this approach is that using the taskRepo repository allows us to use the same coding style for both the frontend and backend, making it easier for us as developers to switch back and forth.

Step 2: Register the Controller

Head over to the backend/index.ts file and register the controller:

export const api = remultExpress({
  entities: [Task],
  controllers: [TasksController],
  initApi: async () => {
    //...
  },
})

Code Explanation

• By adding controllers: [TasksController], we make the TasksController available for API calls from the frontend.

Step 3: Adjust the Frontend

Adjust the frontend/Todo.tsx component to call the backend method:

async function setAllCompleted(completed: boolean) {
  await TasksController.setAllCompleted(completed)
}

Code Explanation

• We removed the for loop and the direct update calls from the frontend.
• We now call TasksController.setAllCompleted(completed) to perform the updates on the backend.
• After the backend method completes, we refresh the task list by calling taskRepo.find().then(setTasks).
• An advantage of this approach is that the call to setAllCompleted is strongly typed, protecting us from spelling or typing mistakes using TypeScript.

Try It Out

Click the “Set All Completed” and “Set All Uncompleted” buttons to see the improved performance with the backend method handling the updates.