When a standard language feature already does the job, use it instead of a manual or custom reimplementation — this is clearer, less error-prone, and easier to maintain. Examples observed in review: - Use `Array.isArray(x)` instead of a hand-rolled `isArray()` helper. - Use `str.endsWith('...')` instead of `str.slice(-3) === '...'` plus a redundant length check. - Use `str.startsWith('--no-')` instead of `flags.indexOf('--no-') !== -1`, since `indexOf` can match the substring anywhere, not just at the start. - Use default function parameters instead of manually checking for `undefined`: ```js // instead of allowExcessArguments(allowExcess) { if (allowExcess === undefined) allowExcess = true; ... } // prefer allowExcessArguments(allowExcess = true) { ... } ``` - Use `Object.prototype.hasOwnProperty.call(obj, key)` instead of the `in` operator when you only want to check the object's own properties (the `in` operator also matches inherited properties). - When adding case-insensitivity or other variants to a regex, prefer a targeted character class (e.g. `[eE]`) over a blanket `/i` flag, so the intent of what varies is explicit rather than silently affecting the whole pattern. Before writing custom logic, check whether a native method or language feature already covers the case; it communicates intent more clearly to readers and avoids subtle bugs from incomplete reimplementations.