Array destructuring
var [a,b] = [1,2]
var [a,b] = c //c=[1,2]
Object destructuring
var {a,b} = {a : 1, b : 2}
({a,b} = {a : 1, b : 2})
var {a,b} = c //c={a : 1 , b : 2}
({a,b} = c)
also provide support for default values, assigning to new variable names
关于Object destructing
Object的key用于匹配，左边的value应该是一个变量，右边的value应该有一个值。var {c} = {c:1}实际上是var {c:c} = {c:1}，key和value相同的时候可以简写是es6的语法糖。
