Learn ECMAScript - Second Edition

The isExtensible(target) method

The isExtensible trap is executed when we check if the object is extensible or not, using the Object.isExtensible() method. It takes only one parameter--that is, the target object. It must return a Boolean value indicating whether the object is extensible or not.

Here is a code example that demonstrates how to use the isExtensible trap:

const proxy = new Proxy({age: 12}, { isExtensible(target) {     return Object.isExtensible(target); } }); console.log(Reflect.isExtensible(proxy)); //Output "true"