ECMAScript6中Set/WeakSet详解

var s1 = new Set()
s1.add(1)
s1.add(2)
s1.add(3)
s1.add(1)
 
var s2 = new Set()
s2.add('a')
s2.add('a')
 
// 输出1，2, 3
for (var i of s1 ) {
  console.log(i)
}
// 输出a
for (var i of s2 ) {
  console.log(i)
}

var s3 = new Set([1,2,3,1])
s3.size // 3

var s4 = new Set()
s4.add({})
s4.add({})
s4.size // 2

var s1 = new Set()
s1.add(1)
s1.add(2)
s1.add(3)
 
// 输出1，2, 3
for (var i of s1) {
  console.log(i)
}

var s1 = new Set()
s1.add(1)
s1.add(2)
 
// toArray
var a1 = Array.from(s1)
Array.isArray(a1) // true
 
// or
var a1 = [...new Set(s1)]　

function distinct(arr) {
  return Array.from(new Set(arr))
// return [...new Set(arr)]
}

ws = new WeakSet()
ws.add(1)

ws = new WeakSet()
ws.size // undefined
ws.forEach // undefined