Reflect.has() vs Reflect.isExtensible()
Reflect.has() and Reflect.isExtensible() are both JavaScript Reflect APIs, and choosing between them is a common point of confusion. This page compares their syntax, parameters, return values, and typical use cases so you can pick the right one. Reflect.has(): Like the in operator. Its syntax is Reflect.has(target, property). Reflect.isExtensible(): Checks if target is extensible. Its syntax is Reflect.isExtensible(target). Example of Reflect.has(): Reflect.has({x:1}, "x") // true. Example of Reflect.isExtensible(): Reflect.isExtensible({}) // true. Read the full references for Reflect.has() and Reflect.isExtensible() to see edge cases, time complexity, browser support, and the mistakes developers most often make with each. Other Reflect APIs worth comparing: Reflect.get(), Reflect.set(), Reflect.preventExtensions(), Reflect.getOwnPropertyDescriptor(), Reflect.defineProperty(), Reflect.getPrototypeOf(). Both belong to the Reflect category in the JS Reference documentation, which covers 9 entries in total. Try both in the JavaScript playground to see the behavioral difference live.