How to filter nested array of object?

Question

I'm struggling with filtering a nested array of objects. My expected result, I want to get a user who has an email address that starts with the mil (example) letter or I want to get user who has female gender. I have seen tricks from another question but I still don't get my expected result.

Let's say my data is below:

let users = [{
    "results": [{
        "gender": "female",
        "name": {
          "title": "Miss",
          "first": "Britney",
          "last": "Sims"
        },
        "email": "[email protected]",
        "login": {
          "uuid": "2d5afd5e-a598-469f-9933-4edba18bcefb",
          "username": "blueelephant921",
          "password": "ccccccc",
          "salt": "uJHyJ9ZL",
          "md5": "5724c4fbd97e5155d19f71a44f12cc48",
          "sha1": "85dff52890cee9977409fc6ae332a7e2326d6aa4",
          "sha256": "ab62d511f943bfca48935cb4620b3b2007f8d1b9c1e04a04ea76ea95cd099d5f"
        },
        "registered": {
          "date": "2014-05-20T20:54:39.692Z",
          "age": 8
        }
      },
      {
        "gender": "female",
        "name": {
          "title": "Ms",
          "first": "Imogen",
          "last": "Edwards"
        },
        "email": "[email protected]",
        "login": {
          "uuid": "5a79ebec-08a6-45de-a2de-b3222f0d1ffe",
          "username": "silversnake277",
          "password": "clifford",
          "salt": "7d1g093S",
          "md5": "585e4a480fb97e0f7430ace6acaabd4f",
          "sha1": "c2214f29692ca2aea5898f7c9e40846e125c5657",
          "sha256": "6ec460f8cbc394e7758f22bbe185c5ae54048e1924fad1b94ac2511511ec2b5a"
        },
        "registered": {
          "date": "2016-04-10T14:57:49.011Z",
          "age": 6
        }
      }
    ],
    "info": {
      "seed": "foobar",
      "results": 10,
      "page": 1,
      "version": "1.3"
    }
  },
  {
    "results": [{
        "gender": "female",
        "name": {
          "title": "Miss",
          "first": "Avery",
          "last": "Harris"
        },
        "email": "[email protected]",
        "login": {
          "uuid": "36213f8d-ab68-4906-b215-5660c84ffbf2",
          "username": "greengoose482",
          "password": "amazon",
          "salt": "SAFLaz7k",
          "md5": "99b57bab46e91f99e28f9920a70789db",
          "sha1": "ed0faee69842302e732f92f6d06f44d97f3c617e",
          "sha256": "ebcccbab0ce22a2ee5f5caa0f88abbbc58e1fc89829bf30ebfe81b839c0aca1a"
        },
        "registered": {
          "date": "2002-05-16T09:53:41.802Z",
          "age": 20
        }
      },
      {
        "gender": "male",
        "name": {
          "title": "Mr",
          "first": "Milton",
          "last": "Miles"
        },
        "email": "[email protected]",
        "login": {
          "uuid": "b16bf03e-daa8-46b9-8c8c-6fe605abaa63",
          "username": "brownpanda533",
          "password": "gggg",
          "salt": "4zdtNQQO",
          "md5": "5415ef33797665bc91103cc28e10c127",
          "sha1": "00816e03d999d456524abf9a3f1229d930c2ca37",
          "sha256": "da3db1d7fe779b4c2c5ceebefa60c43a2d5eacb0a31ed8305b52859db82a100d"
        },
        "registered": {
          "date": "2012-02-11T18:46:12.048Z",
          "age": 10
        }
      }
    ],
    "info": {
      "seed": "foobar",
      "results": 10,
      "page": 2,
      "version": "1.3"
    }
  }
]

const findUser = users.filter((u) =>
  u.results.some((i) => i.email.startsWith("mil"))
);
console.log(findUser);

From my current code, I just have the data as is.

Do you want a single user or all who match? Do you only want gender: female if there are no matches for email: mil...? — D M
– D M, Commented Apr 19, 2022 at 0:18
@DM Who all match. Possibly I want add more than one criteria. — syaifulhusein
– syaifulhusein, Commented Apr 19, 2022 at 1:01

CertainPerformance · Accepted Answer · 2022-04-19 02:42:01Z

If you want to get users, then filter alone isn't quite the right approach, because then you'll get an array of arrays of users, not an array of users. First flatten all the results into a single array, then filter that array (which is now composed of users).

let users=[{results:[{gender:"female",name:{title:"Miss",first:"Britney",last:"Sims"},email:"[email protected]",login:{uuid:"2d5afd5e-a598-469f-9933-4edba18bcefb",username:"blueelephant921",password:"ccccccc",salt:"uJHyJ9ZL",md5:"5724c4fbd97e5155d19f71a44f12cc48",sha1:"85dff52890cee9977409fc6ae332a7e2326d6aa4",sha256:"ab62d511f943bfca48935cb4620b3b2007f8d1b9c1e04a04ea76ea95cd099d5f"},registered:{date:"2014-05-20T20:54:39.692Z",age:8}},{gender:"female",name:{title:"Ms",first:"Imogen",last:"Edwards"},email:"[email protected]",login:{uuid:"5a79ebec-08a6-45de-a2de-b3222f0d1ffe",username:"silversnake277",password:"clifford",salt:"7d1g093S",md5:"585e4a480fb97e0f7430ace6acaabd4f",sha1:"c2214f29692ca2aea5898f7c9e40846e125c5657",sha256:"6ec460f8cbc394e7758f22bbe185c5ae54048e1924fad1b94ac2511511ec2b5a"},registered:{date:"2016-04-10T14:57:49.011Z",age:6}}],info:{seed:"foobar",results:10,page:1,version:"1.3"}},{results:[{gender:"female",name:{title:"Miss",first:"Avery",last:"Harris"},email:"[email protected]",login:{uuid:"36213f8d-ab68-4906-b215-5660c84ffbf2",username:"greengoose482",password:"amazon",salt:"SAFLaz7k",md5:"99b57bab46e91f99e28f9920a70789db",sha1:"ed0faee69842302e732f92f6d06f44d97f3c617e",sha256:"ebcccbab0ce22a2ee5f5caa0f88abbbc58e1fc89829bf30ebfe81b839c0aca1a"},registered:{date:"2002-05-16T09:53:41.802Z",age:20}},{gender:"male",name:{title:"Mr",first:"Milton",last:"Miles"},email:"[email protected]",login:{uuid:"b16bf03e-daa8-46b9-8c8c-6fe605abaa63",username:"brownpanda533",password:"gggg",salt:"4zdtNQQO",md5:"5415ef33797665bc91103cc28e10c127",sha1:"00816e03d999d456524abf9a3f1229d930c2ca37",sha256:"da3db1d7fe779b4c2c5ceebefa60c43a2d5eacb0a31ed8305b52859db82a100d"},registered:{date:"2012-02-11T18:46:12.048Z",age:10}}],info:{seed:"foobar",results:10,page:2,version:"1.3"}}];

const allUsers = users.flatMap(({ results }) => results);
const femaleOrMilUsers = allUsers.filter(u => u.email.startsWith('mil') || u.gender === 'female');
console.log(femaleOrMilUsers);

If you want to change the existing structure, and mutate the results array so that only the matching users are included, iterate over each object in the outer array and reassign the results property to the filtered array.

let users=[{results:[{gender:"female",name:{title:"Miss",first:"Britney",last:"Sims"},email:"[email protected]",login:{uuid:"2d5afd5e-a598-469f-9933-4edba18bcefb",username:"blueelephant921",password:"ccccccc",salt:"uJHyJ9ZL",md5:"5724c4fbd97e5155d19f71a44f12cc48",sha1:"85dff52890cee9977409fc6ae332a7e2326d6aa4",sha256:"ab62d511f943bfca48935cb4620b3b2007f8d1b9c1e04a04ea76ea95cd099d5f"},registered:{date:"2014-05-20T20:54:39.692Z",age:8}},{gender:"female",name:{title:"Ms",first:"Imogen",last:"Edwards"},email:"[email protected]",login:{uuid:"5a79ebec-08a6-45de-a2de-b3222f0d1ffe",username:"silversnake277",password:"clifford",salt:"7d1g093S",md5:"585e4a480fb97e0f7430ace6acaabd4f",sha1:"c2214f29692ca2aea5898f7c9e40846e125c5657",sha256:"6ec460f8cbc394e7758f22bbe185c5ae54048e1924fad1b94ac2511511ec2b5a"},registered:{date:"2016-04-10T14:57:49.011Z",age:6}}],info:{seed:"foobar",results:10,page:1,version:"1.3"}},{results:[{gender:"female",name:{title:"Miss",first:"Avery",last:"Harris"},email:"[email protected]",login:{uuid:"36213f8d-ab68-4906-b215-5660c84ffbf2",username:"greengoose482",password:"amazon",salt:"SAFLaz7k",md5:"99b57bab46e91f99e28f9920a70789db",sha1:"ed0faee69842302e732f92f6d06f44d97f3c617e",sha256:"ebcccbab0ce22a2ee5f5caa0f88abbbc58e1fc89829bf30ebfe81b839c0aca1a"},registered:{date:"2002-05-16T09:53:41.802Z",age:20}},{gender:"male",name:{title:"Mr",first:"Milton",last:"Miles"},email:"[email protected]",login:{uuid:"b16bf03e-daa8-46b9-8c8c-6fe605abaa63",username:"brownpanda533",password:"gggg",salt:"4zdtNQQO",md5:"5415ef33797665bc91103cc28e10c127",sha1:"00816e03d999d456524abf9a3f1229d930c2ca37",sha256:"da3db1d7fe779b4c2c5ceebefa60c43a2d5eacb0a31ed8305b52859db82a100d"},registered:{date:"2012-02-11T18:46:12.048Z",age:10}}],info:{seed:"foobar",results:10,page:2,version:"1.3"}}];

for (const obj of users) {
  obj.results = obj.results.filter(u => u.email.startsWith('mil') || u.gender === 'female');
}
console.log(users);

It works. But I still want the data structure not to change. I want the structure like the above. How?
What do you mean exactly? Your question said that you wanted users for which the email or the gender matches. This retrieves such users.

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