promises

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.

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.