destructuring.js

// list matching
var [a, , b] = [1,2,3];

console.log(a);
console.log(b);

[a, b, ...rest] = [10, 20, 30, 40, 50];
console.log(a); // 10
console.log(b); // 20
console.log(rest); // [30, 40, 50]

//Default values
var a, b;
[a=5, b=7] = [1];
console.log(a); // 1
console.log(b); // 7


//Assigning to new variables names and providing default values
var {a:aa = 10, b:bb = 5} = {a: 3};

console.log(aa); // 3
console.log(bb); // 5

//Setting a function parameter's default value
function drawChart({size = 'big', cords = {x: 0, y: 0}, radius = 25} = {}) {
  console.log(size, cords, radius);
}

drawChart({
  cords: {x: 18, y: 30},
  radius: 30
});



//Nested object and array destructuring
var metadata = {
    title: 'Scratchpad',
    translations: [
       {
        locale: 'de',
        localization_tags: [],
        last_edit: '2014-04-14T08:43:37',
        url: '/de/docs/Tools/Scratchpad',
        title: 'JavaScript-Umgebung'
       }
    ],
    url: '/en-US/docs/Tools/Scratchpad'
};

var {title: englishTitle, translations: [{title: localeTitle}]} = metadata;

console.log(englishTitle); // "Scratchpad"
console.log(localeTitle);  // "JavaScript-Umgebung"






// For of iteration and destructuring
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);
}






//Unpacking fields from objects passed as function parameter
function userId({id}) {
  return id;
}

function whois({displayName, fullName: {firstName: name}}) {
  console.log(displayName + ' is ' + name);
}

var user = { 
  id: 42, 
  displayName: 'jdoe',
  fullName: { 
      firstName: 'John',
      lastName: 'Doe'
  }
};

console.log('userId: ' + userId(user)); // "userId: 42"
whois(user); // "jdoe is John"