数组查重

1、纯数组（不含对象或子数组）

var array = [1,2,3,3,4,5];
console.log(Array.from(new Set(array)))
//输出
[1, 2, 3, 4, 5]

2、含对象或子数组的

function ret(arr) {
  const res = [];
  const json = {};

  for (let i = 0; i < arr.length; i++) {
    if (!json[arr[i].id]) {
      res.push(arr[i]);
        json[arr[i].id] = arr[i].id;
       }
    }

    return res;
  }

const arr = [
  {
    id: 1,
    name: "张三"
  },
  {
    id: 1,
    name: "张三"
  }
];

ret(arr);

 3、去重并且合并对象

function ret(arr) {
  const res = [];
  const json = {};

  for (let i = 0; i < arr.length; i++) {
    var ai = arr[i];
    if (!json[ai.id]) {
      res.push(ai);
      json[ai.id] = ai.id;
    }else{
      for (var j = 0; j < res.length; j++) {
        var dj = res[j];
        if (dj.id=== ai.id) {
          dj.val = dj.val.concat(ai.val); // 也可以写其它合并代码
          break;
         }
      }
    }

    return res;
  }

const arr = [
  {
    id: 1,
    name: "张三",
    val: [
      a: 1
    ]
  },
  {
    id: 1,
    name: "张三",
    val: [
      b: 2
    ]
  }
];

ret(arr);