SOURCE

const s=new Set([1,2,3]);
console.log(s);  //Set(3) {1, 2, 3}
console.log(s.size);  //3

s.add('a').add('b').add('c');
console.log(s);  //Set(6){1,2,3,'a','b','c'}

console.log(s.delete('a'));  //true

console.log(s.has('a'));  //false

// s.clear();
// console.log(s);  //Set(0){}

console.log(s.keys());
console.log(s.values());

console.log(s.entries()); //返回键值对

s.forEach(function(value,key,set){
  console.log(value+'miaov');
});
console.log(s);