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ObjectObject.preventExtensionsbeginner

Object.preventExtensions() — basics

📖 Usage Example
// Prevent new properties from being added
const obj = { a: 1 }
Object.preventExtensions(obj)
obj.b = 2    // silently ignored
Object.keys(obj)   // → ['a']

Use Object.preventExtensions() to lock an object so no new properties can be added, while still allowing modifications to existing ones.

Object.preventExtensions()

Object.preventExtensions(obj) prevents new properties from being added to an object. Existing properties can still be modified or deleted.

Challenge: Implement lockShape(obj) that prevents new properties from being added to the object.

💡 Hints (1)
  • • preventExtensions only blocks adding new properties, not modifying or deleting existing ones