handler.deleteProperty()

The following parameters are passed to the deleteProperty() method. this is bound to the handler.

target

The target object.

property

The name or Symbol of the property to delete.

The deleteProperty() method must return a boolean value indicating whether or not the property has been successfully deleted.

This trap can intercept these operations:

• The delete operator: delete proxy[foo] and delete proxy.foo
• Reflect.deleteProperty()

Or any other operation that invokes the [[Delete]] internal method.

If the following invariants are violated, the trap throws a TypeError when invoked.

• A property cannot be deleted, if it exists as a non-configurable own property of the target object.

The following code traps the delete operator.

const p = new Proxy(
  {},
  {
    deleteProperty(target, prop) {
      if (!(prop in target)) {
        console.log(`property not found: ${prop}`);
        return false;
      }
      delete target[prop];
      console.log(`property removed: ${prop}`);
      return true;
    },
  },
);

p.a = 10;
console.log("a" in p); // true

const result1 = delete p.a; // "property removed: a"
console.log(result1); // true
console.log("a" in p); // false

const result2 = delete p.a; // "property not found: a"
console.log(result2); // false

• Proxy
• Proxy() constructor
• delete
• Reflect.deleteProperty()