Reflect.preventExtensions()

The static Reflect.preventExtensions() method prevents new properties from ever being added to an object (i.e., prevents future extensions to the object). It is similar to Object.preventExtensions(), but with some differences.

target

The target object on which to prevent extensions.

A Boolean indicating whether or not the target was successfully set to prevent extensions.

A TypeError, if target is not an Object.

The Reflect.preventExtensions() method allows you to prevent new properties from ever being added to an object (i.e., prevents future extensions to the object). It is similar to Object.preventExtensions().

See also Object.preventExtensions().

// Objects are extensible by default.
let empty = {}
Reflect.isExtensible(empty)  // === true

// ...but that can be changed.
Reflect.preventExtensions(empty)
Reflect.isExtensible(empty)  // === false

If the target argument to this method is not an object (a primitive), then it will cause a TypeError. With Object.preventExtensions(), a non-object target will be coerced to an object.

Reflect.preventExtensions(1)
// TypeError: 1 is not an object

Object.preventExtensions(1)
// 1

• Polyfill of Reflect.preventExtensions in core-js
• Reflect
• Object.isExtensible()