Javascript - Multidimensional array object to array

Question

I'm new to Node.js and I want to access a particular set of information from an object that looks like this:

userData: [
  {
    value: false,
    id: 1,
    title: 'Hello World',
    date: '17 February 2018 - 06:27:51 PM',
    status: 'Processing'
  },
  {
    value: false,
    id: 2,
    title: 'Hello People',
    date: '17 February 2018 - 06:27:48 PM',
    status: 'Active'
  },
  {
    value: false,
    id: 3,
    title: 'Hello Canary',
    date: '17 February 2018 - 06:27:44 PM',
    status: 'Expired'
  }
]

Now I want to return an array that consist of only "title"

Example: ['Hello World', 'Hello people', 'Hello Canary']

I have tried Object.values(obj) and Object.keys(yourObject).map(key => yourObject[key]) without any luck. Can anyone please help me?

Update: I'm using ES6 and would like to optimize my code for performance

Possible duplicate of From an array of objects, extract value of a property as array — Heretic Monkey
– Heretic Monkey, Commented Mar 1, 2018 at 17:10
@MikeMcCaughan No luck with var result = objArray.map(a => a.foo); — Dev Aggarwal
– Dev Aggarwal, Commented Mar 1, 2018 at 17:31

Helam · Accepted Answer · 2018-03-01 17:16:54Z

4

let titles = userData.map(x => x.title);

When using Array.prototype.map with an array. It returns an array made up of the return value of the function you pass it, called on each element of the array. So the above example, when used on your array of objects containing the .title property, will return a new array containing the titles of each object in the original array.

edited Mar 1, 2018 at 17:16

answered Mar 1, 2018 at 17:08

Helam

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2 Comments

Dipak Over a year ago

Your answer is partially right and it will require reassigning the processed output that is a reason I gave the downvote to you.

Dev Aggarwal Over a year ago

I tired using return userData.map(x => x.title) in a function. Here's the error for the same: TypeError: Cannot read property 'header' of undefined

Abhijit Kar ツ · Accepted Answer · 2018-03-01 17:16:38Z

2

Here's a working snippet

var userData = [{
    value: false,
    id: 1,
    title: 'Hello World',
    date: '17 February 2018 - 06:27:51 PM',
    status: 'Processing'
  },
  {
    value: false,
    id: 2,
    title: 'Hello People',
    date: '17 February 2018 - 06:27:48 PM',
    status: 'Active'
  },
  {
    value: false,
    id: 3,
    title: 'Hello Canary',
    date: '17 February 2018 - 06:27:44 PM',
    status: 'Expired'
  }
]

// Solution to your problem
let titles = userData.map(function(obj) {
  return obj.title;
});

console.log(titles);

Explanation:

Map will execute on each object of the User Data array
Map method takes in a function which returns values that we want in our final array, which is, in this case 'title'
So after Map is done iterating through the whole list, titles of each object in the User Data array, will be collected in titles variable

edited Mar 1, 2018 at 17:16

answered Mar 1, 2018 at 17:10

Abhijit Kar ツ

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3 Comments

Dev Aggarwal Over a year ago

Thank you for the explanation

Dev Aggarwal Over a year ago

I got it working. I was using Camel case in property. Silly me :D

Abhijit Kar ツ Over a year ago

Good to hear that. :D

Bimlendu Kumar · Accepted Answer · 2018-03-01 17:20:02Z

0

Try this:
var userData =  [
        {
          value: false,
          id: 1,
          title: 'Hello World',
          date: '17 February 2018 - 06:27:51 PM',
          status: 'Processing'
        },
        {
          value: false,
          id: 2,
          title: 'Hello People',
          date: '17 February 2018 - 06:27:48 PM',
          status: 'Active'
        },
        {
          value: false,
          id: 3,
          title: 'Hello Canary',
          date: '17 February 2018 - 06:27:44 PM',
          status: 'Expired'
        }
      ];
      var newArray=[];
userData.forEach(function(entry) {
    newArray.push(entry.title);
});
alert(newArray);

answered Mar 1, 2018 at 17:20

Bimlendu Kumar

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