modern-javascript-patterns

Wrap callback-based operations in Promises, then use async functions with await to consume them. Handle errors with try/catch blocks instead of error-first callbacks, and use Promise.all for parallel execution of independent operations.

Promise.all rejects immediately when any promise fails, while Promise.allSettled waits for all promises to complete and returns each result with a fulfilled or rejected status. Use allSettled when you need every outcome regardless of individual failures.

Use the nullish coalescing operator (??) when 0, empty string, or false are valid values, since it only defaults on null or undefined. Logical OR (||) treats all falsy values as missing, which causes bugs with numeric zero or empty strings.

Yes, optional chaining supports method calls with obj.method?.() and array access with arr?.[0]. It short-circuits to undefined when any part of the chain is null or undefined, preventing 'Cannot read property of undefined' errors.

Traditional functions create their own 'this' binding, so callbacks lose the enclosing context. Arrow functions capture 'this' lexically from the surrounding scope, making them the standard fix for callbacks in class methods and timers.

This approach loses functions, undefined values, Dates, Maps, Sets, and circular references throw errors. Use the built-in structuredClone() function instead, which handles most built-in types and circular structures correctly.