modern-javascript-patterns

Wrap callback-based functions in Promises, then use async/await with try/catch for error handling. For independent async operations, run them in parallel with Promise.all instead of awaiting sequentially to improve performance.

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.

Traditional function expressions lose their 'this' binding when passed as callbacks. Use arrow functions, which capture the lexical 'this' from the enclosing scope, or explicitly bind the function with .bind(this).

Use the spread operator to create shallow copies at each nesting level, or use structuredClone for deep cloning. Avoid JSON.parse(JSON.stringify()) for objects containing functions, Dates, or undefined values since they are lost during serialization.

Async functions silently swallow errors if you forget await or omit try/catch, producing unhandled promise rejections. Always wrap awaited calls in try/catch blocks and avoid wrapping already-async functions in new Promise constructors.