Getting set of values from array based on a condition

Question

I have a JavaScript array as shown below

var userMale = [];
var userData = [
                {userId: "100", userName: "John", gender: "M"},
                {userId: "101", userName: "Emma", gender: "F"},
                {userId: "102", userName: "Alex", gender: "F"},
                {userId: "103", userName: "Sam", gender: "M"}
              ]

I need to get all userIds in to a different array based on gender condition, i.e. All males should be in userMale array

I have written below code to achieve that. It works, however, I am looking to avoid for and if loops

for(var i=0; i<userData.length; i++) {
    if(userData[i].gender == "M") {
        userMale.push(userData[i].userId);
    }
}

console.log("userMale: ", userMale);

Uwe Keim · Accepted Answer · 2018-09-06 18:37:00Z

4

You can use filter.

var userData = [
                {userId: "100", userName: "John", gender: "M"},
                {userId: "101", userName: "Emma", gender: "F"},
                {userId: "102", userName: "Alex", gender: "F"},
                {userId: "103", userName: "Sam", gender: "M"}
              ]
              
let userMale = userData.filter(data => {
  return data.gender === "M"
})

console.log(userMale)

edited Sep 6, 2018 at 18:37

Uwe Keim

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answered Sep 6, 2018 at 16:38

Danijel

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2 Comments

ChilBud Over a year ago

I just need userIds i.e. 100, 103 in the array. Not the entire data

Danijel Over a year ago

Okay, you can append map. let userMale = userData.filter(data => { return data.gender === 'M' }).map((value) => { return value.userId; });

FK82 · Accepted Answer · 2018-09-06 18:36:21Z

1

Since you want to filter and project the elements onto userId at the same time, an approach using Array.reduce seems the best fit. See here:

var userData = [
                {userId: "100", userName: "John", gender: "M"},
                {userId: "101", userName: "Emma", gender: "F"},
                {userId: "102", userName: "Alex", gender: "F"},
                {userId: "103", userName: "Sam", gender: "M"}
              ];
              
const convert = (data) => data.reduce((result, { userId, gender }) => {
  if (gender === 'M') {
    return result.concat(userId);
  } 
  
  return result;
}, []);   

var userMale = convert(userData);

console.log(userMale);

answered Sep 6, 2018 at 18:36

FK82

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1 Comment

rmn Over a year ago

This is a better approach since it needs to loop once rather than twice as in Danijel's answer.

Mohana Naga Venkat Sayempu · Accepted Answer · 2018-09-06 16:42:51Z

1

All you need is using filter function

var userData = [
                    {userId: "100", userName: "John", gender: "M"},
                    {userId: "101", userName: "Emma", gender: "F"},
                    {userId: "102", userName: "Alex", gender: "F"},
                    {userId: "103", userName: "Sam", gender: "M"}
                  ]

    let userMale = userData.filter(data => {
      return data.gender === "M"
    })

    let userFemale = userData.filter(data => {
      return data.gender === "F"
    })

answered Sep 6, 2018 at 16:42

Mohana Naga Venkat Sayempu

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1 Comment

ChilBud Over a year ago

I just need userIds i.e. 100, 103 in the array. Not the entire data

Harun Or Rashid · Accepted Answer · 2018-09-06 16:53:28Z

1

You can use reject of Underscore.js

reject returns the values in list without the elements that the truth test (predicate) passes.

var userMale = _.reject(userData, function(item){ return item.gender != "M"; });

answered Sep 6, 2018 at 16:53

Harun Or Rashid

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Comments

sphinxplayer · Accepted Answer · 2018-09-06 19:39:07Z

Using vanilla JavaScript :

var userData = [
  {userId: "100", userName: "John", gender: "M"},
  {userId: "101", userName: "Emma", gender: "F"},
  {userId: "102", userName: "Alex", gender: "F"},
  {userId: "103", userName: "Sam", gender: "M"}
];

function getMaleFemale ()
{
  // Create an array for each gender
  let male = [], female = [];
  
  // For each user, check if gender is F, if so, push id to female else to male
  userData.forEach( user => ( user.gender === 'F' ? female : male ).push( user.userId ) );
  
  // Return male and female
  return { male, female };
}

// Usage example
let { male, female } = getMaleFemale();

// Do something with male and female

console.log( 'male :', male );
console.log( 'female :', female );

rmn · Accepted Answer · 2018-09-06 20:11:41Z

0

A concise version of FK82's approach.

let userMale = userData.reduce((result, user) =>
    user.gender === 'M' ? result.concat(user.userId) : result
, [])

answered Sep 6, 2018 at 20:11

rmn

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