promises

Learn why using async/await inside JavaScript forEach doesn't wait for promises, causing unhandled rejections and early completion. Fix with for...of, Promise.all, Promise.allSettled for sequential, parallel processing.

Learn best practices to handle specific API errors in JavaScript promise chains, perform redirects without re-renders or store conflicts. Use wrappers, Axios interceptors for centralized fetch error handling in React apps.

Fix Express.js routes returning undefined from Mongoose. Use async/await or .then() with try/catch so res.json sends findById result after promise resolves.