How to find unique elements from 2 array of objects in JS

Question

I have following 2 arrays,

I want to compare empIds value with allEmps id value and want to push unique value to a new array,

var empIds = [ 123, 321 ];

var allEmps = [ [{id: 123, name: 'Raj'}], [{id: 321, name: 'Raju'}], [{id: 931, name: 'Rahul'}];

Expected output:
                [{id: 931, name: 'Rahul'}]

My try,

gridData = [];
empIds.forEach(id => {
  allEmps.forEach(series => {
    if (series[0].id !== id) {
      gridData.push(series[0]);
    }
  });
});

But these code is giving duplicate data also, can anyone pls correct my code.Thanks.

Answer 1

Duplicates are caused by iterating over empIds and over allEmps each time.

Try changing the order and for each employee record checking if it's ID is not in empIds

gridData = [];
allEmps.forEach(series => {
  if (empIds.indexOf(series[0].id) === -1) { // ID not found in empIds
    gridData.push(series[0]);
  }
});
// gridData = [ {id: 931, name: "Rahul"} ]

Answer 2

Try this:

var empIds = [ 123, 321 ];
var allEmps = [ [{id: 123, name: 'Raj'}], [{id: 321, name: 'Raju'}], [{id: 931, name: 'Rahul'}];

var gridData = allEmps.map(arr => arr[0]).filter(emp => !empIds.includes(emp.id)) 

You can do it by steps:

var objs = allEmps.map(arr => arr[0]) 
// returns "[{"id":123,"name":"Raj"},{"id":321,"name":"Raju"},{"id":931,"name":"Rahul"}]"

You don't need to have array inside the array. Then filter the ones that are not part of empIds:

objs.filter(emp => !empIds.includes(emp.id))