/**
 * ES6提供的set 类似于数据中的数组
 * 可以用于扩展运算符 和 for of
 * set:
 * 1.size 返回集合中元素个数
 * 2.add() 增加一个新元素 返回当前集合
 * 3.delete() 删除元素 返回布尔值
 * 4.has() 检查元素中是否包含某个元素 返回布尔值
 * 5.clear() 清空集合 返回undefined
 */

let s = new Set();
console.log(s);
let s1 = new Set([1,2,3,4,5,6,7,8]);
console.log(s1);
console.log(s1.size,'size');
console.log(s1.add(13),'add');
console.log(s1.delete(7),'delete');
console.log(s1.has(12),'has');
console.log(s1.clear(),'clear')
console.log(s1);

var arr = [2,3,4,5,6,7,8,9];
var newArr = new Set(arr);
console.log(newArr,'newArr');
var newArr1 = Array.from(newArr);
console.log(newArr1,'newArr1');

var arr1 = [1,2,2,345,67655,454,31,345,31,39,776,76,88,776];
// 去重
function reduction(arr) {
    let a = new Set(arr);
    return Array.from(a);
}
console.log(reduction(arr1));