How to get the Uniq objects Using javascript or lodash

Question

i am having the Array of objects like this

    var result={
            "employees": [
        {
            "_id": "5796e7a27d075bd0453b7751",
            "firstName": "Test4",
            "schemaName": "Employee"
        },
        {
            "_id": "5796e78e7d075bd0453b774f",
            "firstName": "Test 3",
            "schemaName": "Employee"
        },
        {
            "_id": "5790b203df5ad69025e8a20b",
            "email": "df@gmail.com",
            "schemaName": "Employee"
        },
        {
            "_id": "577f69cc789df5ec1e995513",
            "firstName": "Jeevan",
            "email": "ddd@asd.com",
            "schemaName": "Employee"
        },
        {
            "_id": "577f69cc789df5ec1e995513",
            "firstName": "Chethan",
            "email": "ddd@asd.com",
            "schemaName": "Employee"
        }
    ]
};
    };

but i want uniq objects by email. i am using lodash uniq but its Not giving proper Result. here i tried this code.

var combined=result.employees.map(function(employee){
    employee.schemaName='Employee';
    return employee;
});
combined = _.uniq(combined, 'email');
console.log(combined);

The Result is coming like this.

   [ { _id: '5796e7a27d075bd0453b7751',
    firstName: 'Test4',
    schemaName: 'Employee' },
  { _id: '5790b203df5ad69025e8a20b',
    email: 'df@gmail.com',
    schemaName: 'Employee' },
  { _id: '577f69cc789df5ec1e995513',
    firstName: 'Jeevan',
    email: 'ddd@asd.com',
    schemaName: 'Employee' } ]

i want the objects which are not having email ids and i want only objects which are unique emailid's can anybody help me on this. I want the Result contain the objects Which are not having email id also. The Result should be like this.

[ { _id: '5796e7a27d075bd0453b7751',
    firstName: 'Test4',
    schemaName: 'Employee' },
{ _id: '5796e78e7d075bd0453b774f',
    firstName: 'Test3',
    schemaName: 'Employee' },
  { _id: '5790b203df5ad69025e8a20b',
    email: 'df@gmail.com',
    schemaName: 'Employee' },
  { _id: '577f69cc789df5ec1e995513',
    firstName: 'Jeevan',
    email: 'ddd@asd.com',
    schemaName: 'Employee' } ]

Answer 1

I'm using a deepEquals algorithm so this code becomes more general. If you want to check only by email, just change the equals function below.

const equals =
  // Naïve deepEquals, only for demo. Doesn't work if keys orders vary.
  (obj1, obj2) => JSON.stringify(obj1) === JSON.stringify(obj2);

  // A real deepEquals:
  // https://www.npmjs.com/package/fast-deep-equal

const uniq = (el1, index1, array) =>
  array.every((el2, index2) => index1 <= index2 || !equals(el1, el2));

[{ a: 1, b: 2 }, { c: 3 }, { a: 1, b: 2 }, { d: 4 }, { a: 1, b: 2 }].filter(uniq);
// Result: [ { a: 1, b: 2 }, { c: 3 }, { d: 4 } ]

Answer 2

I would recommend the use of _.uniqWith for this with your own comparator.

var result = {
    "employees": [
        {
            "_id": "5796e7a27d075bd0453b7751",
            "firstName": "Test4",
            "lastName": "T",
            "__v": 0,
            "schemaName": "Employee"
        },
        {
            "_id": "5796e78e7d075bd0453b774f",
            "firstName": "Test 3",
            "lastName": "T",
            "__v": 0,
            "schemaName": "Employee"
        },
        {
            "_id": "5796e77e7d075bd0453b774d",
            "firstName": "Test 2",
            "lastName": "T",
            "__v": 0,
            "documents": [],
            "schemaName": "Employee"
        },
        {
            "_id": "5796e7707d075bd0453b774b",
            "firstName": "Test1",
            "lastName": "T",
            "__v": 0,
            "schemaName": "Employee"
        },
        {
            "_id": "5790b203df5ad69025e8a20b",
            "firstName": "Ganesh",
            "lastName": "dsf",
            "__v": 0,
            "email": "df@gmail.com",
            "schemaName": "Employee"
        },
        {
            "_id": "577f69cc789df5ec1e995513",
            "firstName": "Jeevan",
            "__v": 0,
            "email": "fs@asf.com",
            "schemaName": "Employee"
        },
        {
            "_id": "577f69cc789df5ec1e995513",
            "firstName": "Chethan",
            "__v": 0,
            "email": "fs@asf.com",
            "schemaName": "Employee"
        }
    ]
};

// Create a lodash chain from the employees.
combined = _.uniqWith(result.employees, function(e1, e2){
  return e1.email && e1.email === e2.email;
});

console.log(combined);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.14.0/lodash.min.js"></script>

Answer 3

This could make it too.

_.uniqBy(result.employees, function(employee){return employee.email || employee._id;});