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/*
The destructuring assignment syntax is a JavaScript expression that makes it possible to 
extract data from arrays or objects into distinct variables.
*/

var a, b, rest;
[a, b] = [1, 2]
console.log(a) // 1
console.log(b) // 2

[a, b, ...rest] = [1, 2, 3, 4, 5]
console.log(a) // 1
console.log(b) // 2
console.log(rest) // [3, 4, 5]

({a, b} = {a:1, b:2})
console.log(a) // 1
console.log(b) // 2

/*
The object and array literal expressions provide an easy way to create ad hoc packages of data
var x = [1, 2, 3, 4, 5]

The destructuring assignment uses similar syntax, but on the left-hand side of the assignment 
to define what elements to extract from the sourced variable.
*/
var x = [1, 2, 3, 4, 5]
var [y, z] = x
console.log(y); // 1
console.log(z); // 2

// default values
var a, b;

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

// Parsing an array returned from a function

function f() {
  return [1, 2];
}

var a, b; 
[a, b] = f(); 
console.log(a); // 1
console.log(b); // 2

// Ignoring some returned values
function f() {
  return [1, 2, 3];
}

var [a, , b] = f();
console.log(a); // 1
console.log(b); // 3

// ignore all values
[,,] = f();

// object destructuring
var o = {p: 42, q: true};
var {p, q} = o;

console.log(p); // 42
console.log(q); // true