Setting Array.prototype.length doesn't explicitly tell you which properties got deleted

repro.js

const proxy = new Proxy ( [0, 1, 2], {
  get: ( ...args ) => {
    console.log ( '[get]', ...args );
    return Reflect.get ( ...args );
  },
  apply: ( ...args ) => {
    console.log ( '[apply]', ...args );
    return Reflect.apply ( ...args );
  },
  construct: ( ...args ) => {
    console.log ( '[construct]', ...args );
    return Reflect.construct ( ...args );
  },
  defineProperty: ( ...args ) => {
    console.log ( '[defineProperty]', ...args );
    return Reflect.defineProperty ( ...args );
  },
  deleteProperty: ( ...args ) => {
    console.log ( '[deleteProperty]', ...args );
    return Reflect.deleteProperty ( ...args );
  },
  getOwnPropertyDescriptor: ( ...args ) => {
    console.log ( '[getOwnPropertyDescriptor]', ...args );
    return Reflect.getOwnPropertyDescriptor ( ...args );
  },
  getPrototypeOf: ( ...args ) => {
    console.log ( '[getPrototypeOf]', ...args );
    return Reflect.getPrototypeOf ( ...args );
  },
  has: ( ...args ) => {
    console.log ( '[has]', ...args );
    return Reflect.has ( ...args );
  },
  isExtensible: ( ...args ) => {
    console.log ( '[isExtensible]', ...args );
    return Reflect.isExtensible ( ...args );
  },
  ownKeys: ( ...args ) => {
    console.log ( '[ownKeys]', ...args );
    return Reflect.ownKeys ( ...args );
  },
  preventExtensions: ( ...args ) => {
    console.log ( '[preventExtensions]', ...args );
    return Reflect.preventExtensions ( ...args );
  },
  set: ( ...args ) => {
    console.log ( '[set]', ...args );
    return Reflect.set ( ...args );
  },
  setPrototypeOf: ( ...args ) => {
    console.log ( '[setPrototypeOf]', ...args );
    return Reflect.setPrototypeOf ( ...args );
  }
});

proxy.length = 0;

// Output:
// [set] [ 0, 1, 2 ] length 0 [ 0, 1, 2 ]
// [getOwnPropertyDescriptor] [ 0, 1, 2 ] length
// [defineProperty] [ 0, 1, 2 ] length { value: 0 }