dldr

import { load } from 'dldr'; // Mock a simple database interaction const mockDb = { posts: new Map([ ['123', { id: '123', name: 'Post One' }], ['456', { id: '456', name: 'Post Two' }], ['789', { id: '789', name: 'Post Three' }] ]), // Simulates a database call that takes an array of keys execute: async (query: string, keys: string[]): Promise<Array<{ id: string, name: string }>> => { console.log(`[DB] Executing query for keys: ${keys.join(', ')}`); // Simulate network delay await new Promise(resolve => setTimeout(resolve, 50)); return keys.map(key => mockDb.posts.get(key) || { id: key, name: 'Unknown Post' }); } }; // Define the core data loading function that dldr will batch const getPosts = async (keys: string[]): Promise<Array<{ id: string, name: string }>> => { // In a real application, this would be a single database call // that fetches multiple records based on the provided keys. return mockDb.execute('SELECT id, name FROM posts WHERE id IN (?)', keys); }; async function main() { console.log('Demonstrating batching with dldr:\n'); // Request multiple posts concurrently. dldr will batch these into a single call to `getPosts`. const post123Promise = load(getPosts, '123'); const post456Promise = load(getPosts, '456'); // Even if requested again, it's still part of the same batch operation if in the same tick. const post123AgainPromise = load(getPosts, '123'); // Add another request later in the same event loop tick (e.g., from another resolver) // This will still be part of the initial batch await Promise.resolve(); // Ensures other microtasks run, still within the same tick conceptually const post789Promise = load(getPosts, '789'); const loadedPosts = await Promise.all([ post123Promise, post123AgainPromise, post456Promise, post789Promise ]); console.log('\nResults from batched load:'); console.log(loadedPosts); console.log('\nDemonstrating `load.bind` for convenience:'); const loadPost = load.bind(null, getPosts); const boundPostPromise = loadPost('123'); const anotherBoundPostPromise = loadPost('456'); const boundLoadedPosts = await Promise.all([boundPostPromise, anotherBoundPostPromise]); console.log(boundLoadedPosts); } main().catch(console.error);