mutable-object-delete-property.md

const droid = {
  name: 'R2-D2',
  height: '1.08',
  colors: ['blue', 'silver']
}

const newDroid = droid

delete newDroid.colors

//the original object is updated by deleting colors attribute
console.log(droid)
// [object Object] {
//   height: '1.08',
//   name: 'R2-D2'
// }

// newDroid was updated by reference
console.log(newDroid)
// [object Object] {
//   height: '1.08',
//   name: 'R2-D2'
// }