数组或数组对象比较
every() 方法测试一个数组内的所有元素是否都能通过某个指定函数的测试。它返回一个布尔
数组对象：

取交集

  1. let a=[{id:1,a:123,b:1234},{id:2,a:123,b:1234}];
  2. let b=[{id:1,a:123,b:1234},{id:2,a:123,b:1234},{id:3,a:123,b:1234},{id:4,a:123,b:1234}];
  3. let arr = [...b].filter(x => [...a].some(y => y.id === x.id));
  4. console.log('arr',arr)

取差集：

  1. let a=[{id:1,a:123,b:1234},{id:2,a:123,b:1234}];
  2. let b=[{id:1,a:123,b:1234},{id:2,a:123,b:1234},{id:3,a:123,b:1234},{id:4,a:123,b:1234}];
  3. let arr = [...b].filter(x => [...a].every(y => y.id !== x.id));
  4. console.log('arr',arr);

取并集：

  1. let a=new Set([1,2,3,4,5]);
  2. let b=new Set([1,2,3,4,5,6,7,8,9]);
  3. let arr = Array.from(new Set([...a, ...b]));
  4. console.log('arr',arr);

数组包含关系：

  1. var a = [1, 2, 5, 7, 3];
  2. var b = [1, 7, 3];
  3. function isContained(aa, bb) {
  4.     if(!(aa instanceof Array) || !(bb instanceof Array) || ((aa.length < bb.length))) {
  5.         return false;
  6.     }
  7.     for (var i = 0; i < bb.length; i++) {
  8.         var flag = false;
  9.         for(var j = 0; j < aa.length; j++){
  10.             if(a[j] == bb[i]){
  11.                 flag = true;
  12.                  break;
  13.             }
  14.         }
  15.         if(flag == false){
  16.             return flag;
  17.         }
  18.     }
  20.     return true;
  21. }
  22. var c = isContained(a, b);
  23. console.log(c);