JS Built-ins
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ObjectObject.isExtensibleintermediate

Object.isExtensible() — combining checks

📖 Usage Example
// Check if new properties can be added
const obj = { a: 1 }
Object.isExtensible(obj)             // → true
Object.preventExtensions(obj)
Object.isExtensible(obj)             // → false

Use Object.isExtensible() to check whether new properties can still be added to an object.

Object.isExtensible() — combining checks

Use Object.isExtensible() to guard against inadvertently modifying locked objects.

Challenge: Implement safeAddProperty(obj, key, value) that only adds the property if the object is extensible, and returns whether the property was added.

💡 Hints (1)
  • • Check isExtensible before adding properties to avoid silent failures