JS Practice — Built-in Objects

Object.seal() — checking with isSealed

📖 Usage Example

// Prevent adding/removing properties but allow value changes
const obj = Object.seal({ x: 1 })
obj.x = 99     // allowed — value can change
delete obj.x   // silently ignored
obj.x          // → 99

Use Object.seal() to prevent adding or deleting properties on an object while still allowing existing values to be updated.

Object.seal() — verification

Use Object.isSealed(obj) to verify whether an object is sealed.

Challenge: Implement isObjectSealed(obj) that returns whether the object is sealed.

💡 Hints (1)

• isSealed = non-extensible + all properties non-configurable