JS Practice — Built-in Objects

Object.seal() — cannot delete properties

📖 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() — deletion blocked

After sealing, you cannot delete properties from the object (in sloppy mode, the delete silently fails; in strict mode, it throws).

Challenge: Demonstrate that property deletion silently fails on a sealed object.

💡 Hints (1)

• In sloppy mode, delete on sealed objects silently fails