NodeJS: Find object from array not contained in another array

Question

I have two arrays of objects:

var existingUsers1 = [];
    existingUsers1.push({
        "userName": "A",
        "departmentId": "1"
    });
    existingUsers1.push({
        "userName": "B",
        "departmentId": "1"
    });
    existingUsers1.push({
        "userName": "C",
        "departmentId": "1"
    });
    existingUsers1.push({
        "userName": "D",
        "departmentId": "1"
    });

var existingUsers2 = [];
    existingUsers2.push({
        "userName": "A",
        "departmentId": "1"
    });
    existingUsers2.push({
        "userName": "B",
        "departmentId": "1"
    });

I need to find the objects from existingUsers1 that are not present in existingUsers2. Is there any function in nodeJS that I can use to achieve this or any other way?

Possible duplicate of [How to merge two arrays in Javascript and de-duplicate items](https://stackoverflow.com/questions/1584370/how-to-merge-two-arrays-in-javascript-and-de-duplicate-items) — Seblor, Aug 25 '17 at 12:55

Nina Scholz · Accepted Answer · 2017-08-26T16:44:27.820

You could use a Set with Array#filter.

var existingUsers1 = [{ userName: "A", departmentId: "1" }, { userName: "B", departmentId: "1" }, { userName: "C", departmentId: "1" }, { userName: "D", departmentId: "1" }],
    existingUsers2 = [{ userName: "A", departmentId: "1" }, { userName: "B", departmentId: "1" }],
    hash = new Set(existingUsers2.map(o => o.userName)),
    result = existingUsers1.filter(o => !hash.has(o.userName));

console.log(result);

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NodeJS: Find object from array not contained in another array

1 Answers1