JS Built-ins
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ObjectObject.getOwnPropertyDescriptorbeginner

Object.getOwnPropertyDescriptor() — undefined for missing

📖 Usage Example
// Inspect a single property's descriptor
const obj = { x: 42 }
Object.getOwnPropertyDescriptor(obj, 'x')
// → { value: 42, writable: true, enumerable: true, configurable: true }

Use Object.getOwnPropertyDescriptor() to retrieve the descriptor object that describes a property's attributes.

Object.getOwnPropertyDescriptor() — missing property

If the key does not exist on the object (or is inherited), Object.getOwnPropertyDescriptor returns undefined.

Challenge: Implement hasDescriptor(obj, key) that returns true if the descriptor exists, false otherwise.

hasDescriptor({ a: 1 }, 'a')    // → true
hasDescriptor({ a: 1 }, 'b')    // → false
💡 Hints (2)
  • • `getOwnPropertyDescriptor` returns `undefined` for missing **or inherited** properties.
  • • Check `!== undefined` or use optional chaining.