Javascript - retrive a value by key, including nested object

Question

I am trying to write a function that will retrieve a value by key, including searching in nested objects.

Here is as far as I got:

function getByKey (obj, key) {
   if(obj.hasOwnProperty(key)){
         return obj[key];
   }else{
      for(var prop in obj){
          if(typeof prop  == "object" && prop !== null){
             if(prop.hasOwnProperty(key)){
               return prop[key];
             }else{
               return iterate(prop, key);
             }
          }
     }
  }

}

If someone have this function ready and working or can fix my it will be great. If someone knows Underscore function that can do this it will be great.

typeof needs no brackets, null is an object, iterate is missing. — Nina Scholz
– Nina Scholz, Commented Sep 21, 2016 at 13:57
Are you trying to get all values that have this same key? If so call recursively function that goes deep in objects. — Leolian
– Leolian, Commented Sep 21, 2016 at 13:59
Nested objects might hold same keys for different values so which one are you interested in such as the first one, last one or all? — Redu
– Redu, Commented Sep 21, 2016 at 14:32

Nina Scholz · Accepted Answer · 2016-09-21 14:37:12Z

3

You could use an iterative and recursive style to search for the property of an object.

function getByKey(obj, key) {
    function iter(o) {
        if (o !== null && typeof o === 'object') {
            if (key in o) {
                value = o[key];
                return true;
            }
            return Object.keys(o).some(function (k) {
                return iter(o[k]);
            });
        }
    }

    var value;
    iter(obj);
    return value;
}

var o = { a: 1, b: { c: 3, d: 4, e: { f: 5, g: 6 } } }

console.log(getByKey(o, 'f')); // 5
console.log(getByKey(o, 'b')); // { c: ... }
console.log(getByKey(o, 'd')); // 4
console.log(getByKey(o, 'q')); // undefined

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Sep 21, 2016 at 14:37

Nina Scholz

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Comments

Olena Horal · Accepted Answer · 2016-09-21 14:10:09Z

2

Try the following: https://jsfiddle.net/0yqu339t/4/

function getByKey(obj, key) {
      if (obj.hasOwnProperty(key)) {
        return obj[key];
      } else {
        for (var prop in obj) {
          if (typeof(obj[prop]) === "object") {
            return getByKey(obj[prop], key);
          }
        }
      }
    }


    var o = {
      a: 1,
      b: {
        c: 3,
        d: 4,
        e: {
          f: 5,
          g: 6
        }
      }
    }
    console.log(getByKey(o, 'f'));
    console.log(getByKey(o, 'b'));
    console.log(getByKey(o, 'd'));

answered Sep 21, 2016 at 14:10

Olena Horal

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Comments

BenM · Accepted Answer · 2016-09-21 14:03:49Z

1

The problem is you're passing a reference to the key only to the iteration function, but never reference the original object that was passed to it. You need to use obj[prop], as follows:

function getByKey (obj, key) 
{
    if( obj.hasOwnProperty(key) )
    {
        return obj[key];
    }
    else
    {
        for(var prop in obj)
        {
            if( typeof obj[prop] == "object")
            {
                if(obj[prop].hasOwnProperty(key))
                {
                    return obj[prop][key];
                }
                else
                {
                  return getByKey(obj[prop], key);
                }
            }
        }
    }
};

jsFiddle Demo

edited Sep 21, 2016 at 14:03

answered Sep 21, 2016 at 14:01

BenM

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2 Comments

Itsik Mauyhas Over a year ago

Trying and posting the result. thank's for the edit, it was a long day (:

Itsik Mauyhas Over a year ago

It gets error id you don't check that the object is not null, either then that, works great,

Leolian · Accepted Answer · 2016-09-21 14:17:49Z

1

For recursively you can try ( with little help from JQuery )

var haystack = $.map(obj, function(value, index) {
    return [value];
});
var values = []; //or {} depending your situation
var getValues = function( needle, haystack, array ){
    if( haystack[key]) !== 'undefined' ){
      array.push(haystack[key]);
    }else{
      for( var i = 0; i < haystack.length; i++ ){
            getValues( needle , haystack[i], array );
      }
    }
}
getValues( 'key', haystack, values );
console.log(values);  //should be an array [ value1, value2, value3, value4, ... ]
//With all values that have this same searched key

I hope this helps

answered Sep 21, 2016 at 14:17

Leolian

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