去重1

let arr=[{name:1,age:18},{name:2},{name:1,age:18}]
//結果===>[{name:1,age:18},{name:2}]
　function unique(arr) {
      return [...new Set(arr.map(e => JSON.stringify(e)))].map(e => JSON.parse(e))
  }
function unique(arr) {
    const map = new Map()
    return arr.filter( item => !map.has(JSON.stringify(item)) && map.set(JSON.stringify(item), 1))
}
unique(arr)

去重2

let list = [
        { id: "1", content: "A"},
        { id: "2", content: "B"},
        { id: "3", content: "C"},
        { id: "4", content: "D"}
  ];
 let arr = [
        {id: "1",content: "C"},
        {id: "2",content: "D"}
  ];
      function listRemoveRepeat(x) {
        let result = [];
        for (let i = 0; i < x.length; i++) {
          let flag = true;
          let temp = x[i];
          for (let j = 0; j < result.length; j++) {
            // 普通數組 (temp === result[j])
            if (temp.id === result[j].id) {
              flag = false;
              break;
            }
          }
          if (flag) {
            result.push(temp);
          }
        }
        return result;
 }

差集

      function listDifference(x, y) {
        let clone = x.slice(0);
        for (let i = 0; i < y.length; i++) {
          let temp = y[i];
          for (let j = 0; j < clone.length; j++) {
            // 普通數組 (temp === clone[j])
            if (temp.id === clone[j].id) {
              clone.splice(j, 1);
            }
          }
        }
        return listRemoveRepeat(clone);
      }

并集

//調用去重2的方法listRemoveRepeat
 function listConcat(x, y) {
    return listRemoveRepeat(x.concat(y));
}

交集

//調用去重2的方法listRemoveRepeat
function listIntersection(x, y) {
       let result = [];
       for (let i = 0; i < y.length; i++) {
         let temp = y[i];
         for (let j = 0; j < x.length; j++) {
           // 普通數組 (temp === clone[j])
           if (temp.id === x[j].id) {
             result.push(temp);
             break;
           }
         }
       }
       return listRemoveRepeat(result);
}

(參考地址)https://www.cnblogs.com/wyuan-yuan/p/9430105.html