请问如何计算数组中不同元素个数?

Question

预期: arr = ['1','2','3','3'] = > 输出3
预期: arr = ['1','1','1','3'] = > 输入2

Answer 1

console.log([...new Set([5,5,6,6,8,])].length)

数组去重便可得到不同元素的个数, 具体看看数组去重的几种方法

Answer 2

[...new Set(arr)]

Answer 3

(new Set(['1','2','3','3'])).size

Answer 4

var arr = ['1', '2', '3', '3']
let res = arr.reduce(function (a, b) {
  if (!a.includes(b)) a.push(b)
  return a
}, []).length
console.log(res)

Answer 5

var data= arr
    .reduce((pre, cur) => ( pre[cur]++ || ((pre[cur] = 1),(pre.sum++)), pre), {sum:0});
console.log(data.sum)