feat: Adding workers automatically as Svelte compiles

[shahul01]

Describe the problem

Svelte should use workers as more and more system have multi core.
A developer may add worker to use multi threading manually but it could be complicated and its better to move this process to compilation as more and more web apps / web sites will use workers.

Describe the proposed solution

As Svelte compiles, it can add worker automatically to some / all function via wrapper .

opt out -
if in beta, or facing error or just wanting to disable workers, Svelte can have an option in a config to disable(and enable) auto worker mode.

// overview
// general
button → function

// svelte + auto worker mode via wrapper
button → worker → function

Example of how different functions can be used via worker wrapper

// src/lib/workers/workerWrapper.ts
export class WorkerWrapper {
  private worker: Worker;
  private taskCallbacks: Map<string, (data: any) => void>;

  constructor() {
    this.worker = new Worker(
      new URL('./worker.ts', import.meta.url),
      { type: 'module' }
    );
    this.taskCallbacks = new Map();

    this.worker.onmessage = (event) => {
      const { type, data, error } = event.data;
      const callback = this.taskCallbacks.get(type);
      
      if (callback) {
        callback(error || data);
        this.taskCallbacks.delete(type);
      }
    };
  }

  processChartData(data: any[]): Promise<any> {
    return this.postTask('PROCESS_CHART_DATA', data, 'CHART_DATA_PROCESSED');
  }

  validateForm(formData: Record<string, any>): Promise<any> {
    return this.postTask('VALIDATE_FORM', formData, 'FORM_VALIDATED');
  }

  checkPassword(password: string): Promise<any> {
    return this.postTask('CHECK_PASSWORD', password, 'PASSWORD_CHECKED');
  }

  search(query: string, items: any[]): Promise<any> {
    return this.postTask('SEARCH', { query, items }, 'SEARCH_COMPLETED');
  }

  private postTask(type: string, payload: any, responseType: string): Promise<any> {
    return new Promise((resolve, reject) => {
      this.taskCallbacks.set(responseType, (result) => {
        if (result.error) {
          reject(result.error);
        } else {
          resolve(result);
        }
      });

      this.worker.postMessage({ type, payload });
    });
  }

  terminate() {
    this.worker.terminate();
    this.taskCallbacks.clear();
  }
}

// src/lib/workers/worker.ts
type WorkerTask = {
  type: 'PROCESS_CHART_DATA' | 'VALIDATE_FORM' | 'CHECK_PASSWORD' | 'SEARCH';
  payload: any;
};

type WorkerResponse = {
  type: string;
  data: any;
  error?: string;
};

// Chart data processing
function processChartData(data: any[]) {
  try {
    // Example processing
    const processed = data.map(item => ({
      ...item,
      value: Number(item.value),
      timestamp: new Date(item.timestamp).getTime()
    })).sort((a, b) => a.timestamp - b.timestamp);

    return { success: true, data: processed };
  } catch (error) {
    return { success: false, error: (error as Error).message };
  }
}

// Form validation
function validateForm(formData: Record<string, any>) {
  const errors: Record<string, string> = {};
  
  Object.entries(formData).forEach(([field, value]) => {
    if (!value) {
      errors[field] = 'Field is required';
    }
    // Add more validation rules as needed
  });

  return { success: Object.keys(errors).length === 0, errors };
}

// Password strength checker
function checkPasswordStrength(password: string) {
  const checks = {
    length: password.length >= 8,
    hasUpper: /[A-Z]/.test(password),
    hasLower: /[a-z]/.test(password),
    hasNumber: /\d/.test(password),
    hasSpecial: /[!@#$%^&*(),.?":{}|<>]/.test(password),
  };

  const strength = Object.values(checks).filter(Boolean).length;
  let result = 'weak';
  if (strength >= 4) result = 'strong';
  else if (strength >= 3) result = 'medium';

  return { 
    strength: result, 
    checks,
    score: (strength / 5) * 100 
  };
}

// Instant search
function performSearch(query: string, items: any[]) {
  const searchTerm = query.toLowerCase();
  return items.filter(item => 
    Object.values(item).some(value => 
      String(value).toLowerCase().includes(searchTerm)
    )
  );
}

// Main message handler
self.onmessage = async (event: MessageEvent<WorkerTask>) => {
  const { type, payload } = event.data;
  let response: WorkerResponse;

  try {
    switch (type) {
      case 'PROCESS_CHART_DATA':
        response = {
          type: 'CHART_DATA_PROCESSED',
          data: processChartData(payload)
        };
        break;

      case 'VALIDATE_FORM':
        response = {
          type: 'FORM_VALIDATED',
          data: validateForm(payload)
        };
        break;

      case 'CHECK_PASSWORD':
        response = {
          type: 'PASSWORD_CHECKED',
          data: checkPasswordStrength(payload)
        };
        break;

      case 'SEARCH':
        response = {
          type: 'SEARCH_COMPLETED',
          data: performSearch(payload.query, payload.items)
        };
        break;

      default:
        throw new Error(`Unknown task type: ${type}`);
    }

    self.postMessage(response);
  } catch (error) {
    self.postMessage({
      type: 'ERROR',
      error: (error as Error).message,
      data: null
    });
  }
};

export {};

Importance

nice to have

[Rich-Harris]

This doesn't belong in Svelte, it belongs at the level of tools like Vite (which already has built-in support for workers)