for...of iteration and destructuring with an object inside an array

Question

According to the Mozilla docs, here is how to use destructuring inside a for of loop:

var people = [
  {
    name: 'Mike Smith',
    family: {
      mother: 'Jane Smith',
      father: 'Harry Smith',
      sister: 'Samantha Smith'
    },
    age: 35
  },
  {
    name: 'Tom Jones',
    family: {
      mother: 'Norah Jones',
      father: 'Richard Jones',
      brother: 'Howard Jones'
    },
    age: 25
  }
];

for (var {name: n, family: {father: f}} of people) {
  console.log('Name: ' + n + ', Father: ' + f);
}

// "Name: Mike Smith, Father: Harry Smith"
// "Name: Tom Jones, Father: Richard Jones"

My question is, what would the correct destructuring syntax be in case the family object was located inside an array, like this:

var people = [
  {
    name: 'Tom Jones',
    family: [
     {
      mother: 'Norah Jones',
      father: 'Richard Jones',
      brother: 'Howard Jones'
     }
    ],
    age: 25
  }
];

(Note the extra set of [square brackets])

Attempting to destructure using:

for (var {name: n, family[0]: {father: f}} of people) {
  console.log('Name: ' + n + ', Father: ' + f);
}

gives an Unexpected token error at the square bracket.

So in this example, how do I use destructuring to assign a value to f?

Answer 1

You want the array structure represented, not the array index access.

var people = [{
  name: 'Tom Jones',
  family: [{
    mother: 'Norah Jones',
    father: 'Richard Jones',
    brother: 'Howard Jones'
  }],
  age: 25
}];

// Describe the structure -v-----------v
for (var {name: n, family: [{father: f}]} of people) {
  console.log('Name: ' + n + ', Father: ' + f);
}

Of course, this assumes you want only the first member. If you want more, you can use the rest syntax.

var people = [{
  name: 'Tom Jones',
  family: [{
    mother: 'Norah Jones',
    father: 'Richard Jones',
    brother: 'Howard Jones'
  }],
  age: 25
}];

for (var {name: n, family: [{father: f}, ...rem]} of people) {
  console.log('Name: ' + n + ', Father: ' + f);
  console.log("Remaining values: %s", rem.length);
}