Set 物件儲存的值總是唯一的

Set 物件方法

Set 物件作用

• 陣列去重

• var arr = [1,2,3,3,1,4];
  [...new Set(arr)]; // [1, 2, 3, 4]
  Array.from(new Set(arr)); // [1, 2, 3, 4]　　 推薦使用這個去重
   
  
  [...new Set('ababbc')].join(''); // "abc" 字串去重
  new Set('ice doughnut'); //Set(11) {"i", "c", "e", " ", "d", …}

• 並集

• var a = new Set([1, 2, 3]);
  var b = new Set([4, 3, 2]);
  var union = new Set([...a, ...b]); // {1, 2, 3, 4}

• 交集

• var a = new Set([1, 2, 3]);
  var b = new Set([4, 3, 2]);
  var intersect = new
   
   Set([...a].filter(x => b.has(x))); // {2, 3}

• 差集

• var a = new Set([1, 2, 3]);
  var b = new Set([4, 3, 2]);
  var difference = new Set([...a].filter(x => !b.has(x))); // {1}

• 並集