How to access specific value from a nested array within an object array?

Question

I am trying to get a specific field value from a nested array within an object array. I'm assuming I'd use map, but every time I use it in this way I get two empty arrays nested inside two empty objects. I know this is wrong, I'm just showing where my thinking process is going.

function getChildArray(item, index) {
   var x = [item.hobbies]
      return x
}

console.log(parentArray.map(getChildArray))

This is an example of my document structure:

[  
   {  
      "id":12345678900,
      "name":"Jasmin",
      "age":27,
      "hobbies":[  
         {  
            "id":1221,
            "name":"hiking",
            "when":"anytime"
         },
         {  
            "id":9865,
            "name":"eating",
            "when":"all the time"
         }
      ]
   },
   {  
      "id":223456789001,
      "name":"Joe",
      "age":35,
      "hobbies":[  
         {  
            "id":989,
            "name":"gaming",
            "when":"anytime"
         },
         {  
            "id":2355,
            "name":"online gaming",
            "when":"all the time"
         }
      ]
   }
]

How would I, for example, be able to retrieve a list of Joe's hobbies by name only?

@developer033 See also hiking, eating, comma following 989, online gaming — guest271314
– guest271314, Commented Jul 3, 2016 at 4:31

Marco Scabbiolo · Accepted Answer · 2016-07-03 04:10:21Z

2

var joe = parentArray.find(function (item) {
    return item.name === 'Joe';
});

if (joe) {
    var joesHobbiesNames = joe.hobbies.map(function (hobbie) {
       return hobbie.name;
    });
}

Or in ES6

var joe = parentArray.find((item) => item.name === 'Joe');

if (joe) {
    var joesHobbiesNames = joe.hobbies.map((hobbie) => hobbie.name);
}

answered Jul 3, 2016 at 4:10

Marco Scabbiolo

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2 Comments

developer033 Over a year ago

I recommend you to use the filter method instead of find, because if there are several obects with name property "Joe", the find method will return only one object instead of multiple.

Marco Scabbiolo Over a year ago

It was intended to use find instead of filter. The OP asked for JOE's hobbies, not for all the hobbies of all the people called Joe

KevBot · Accepted Answer · 2016-07-03 04:39:44Z

1

Since array.find is not available in all browsers yet, and you may not be using a build tool, here is a complete ES5 way. It uses filter and map:

var data = [{ id: 12345678900, name: 'Jasmin', age: 27, hobbies: [{'id': 1221, 'name': 'hiking', 'when': 'anytime'}, { 'id': 9865, 'name': 'eating', 'when': 'all the time' }] }, { id: 223456789001, name: 'Joe', age: 35, hobbies: [{'id': 989, 'name':
'gaming', 'when': 'anytime'}, { 'id': 2355, 'name': 'online gaming', 'when': 'all the time' }]}];


function getHobbiesByName(name) {
  return data.filter(function(person) {
    return (person.name == name);
  })[0].hobbies.map(function(hobby) {
    return hobby.name
  })
}

console.log(getHobbiesByName('Joe'))

answered Jul 3, 2016 at 4:39

KevBot

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Comments

ElDoRado1239 · Accepted Answer · 2016-07-03 04:15:11Z

0

A quick function to return an item with the desired property and value of that property :

data = [{id:1,name:'Bob',hobbies:['a','b']},{id:2,name:'Alice',hobbies:['c','d']}];

function getPerson(property,value){
 for(var i=0;i<data.length;i++) if(data[i][property] == value) return data[i];
 return {};
}

And a test :

console.log(getPerson('name','Bob'));
console.log(getPerson('name','Bob').hobbies);

answered Jul 3, 2016 at 4:15

ElDoRado1239

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1 Comment

ElDoRado1239 Over a year ago

It returns undefined - also this is just a test, real use would call for checking if the person exists anyway.

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