Extract all values for a single key in a js array of objects

Question

I have a json collection of objects

{  
   "images":{  
      "1":{  
         "image_data":{  
            "votable":true,
            "hashed_filename":"d66f00cf58c4fbbbc9703efff9c7694c"
         },
         "image_reference":1
      },
      "2":{  
         "image_data":{  
            "votable":true,
            "hashed_filename":"5485a21d47e3815cd7f23d5f8a8c8677"
         },
         "image_reference":2
      },
      "3":{  
         "image_data":{  
            "votable":true,
            "hashed_filename":"4df10b887f12d65f2f541c99f0dd1ef8"
         },
         "image_reference":3
      }
   }
}

Is there an easy way to extract the hashed_filename value in a string separated by underscore?

I need a result like d66f00cf58c4fbbbc9703efff9c7694c_5485a21d47e3815cd7f23d5f8a8c8677_4df10b887f12d65f2f541c99f0dd1ef8

Sometimes, sharing why you’re trying to do something helps answerers give you a better answer. — Paul
– Paul, Commented Dec 18, 2017 at 12:43

Bless · Accepted Answer · 2017-12-18 13:16:57Z

6

Yes. Get all values from the object as array, get image_data.hashed_filename from each object in the array, and then join all the values with _.

Object.values(obj.images).map(x => x.image_data.hashed_filename).join('_')

But there are no guarantees on the order of values while evaluating Object.values(obj.images) as objects are unordered in JS.

To order by the keys, get the keys from the object, sort the keys, get the value for each key. Then map over image_data.hashed_filename and join (same as before).

Object.keys(obj.images).sort().map(x => obj.images[x])
  .map(x => x.image_data.hashed_filename).join('_')

edited Dec 18, 2017 at 13:16

answered Dec 18, 2017 at 12:43

Bless

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4 Comments

Roberto Pezzali Over a year ago

And If I want to keep the order?

Mihai Alexandru-Ionut Over a year ago

@RobertoPezzali, just use object.keys method.

Bless Over a year ago

@Alexandru-Ionut Mihai Thanks! Edited.

Bless Over a year ago

@RobertoPezzali Objects are unordered in JS. Updated the answer with a solution to sort by keys.

Titus · Accepted Answer · 2017-12-18 12:46:12Z

Yes, that is possible. You could do something like this:

var o = {  
   "images":{  
      "1":{  
         "image_data":{  
            "votable":true,
            "hashed_filename":"d66f00cf58c4fbbbc9703efff9c7694c"
         },
         "image_reference":1
      },
      "2":{  
         "image_data":{  
            "votable":true,
            "hashed_filename":"5485a21d47e3815cd7f23d5f8a8c8677"
         },
         "image_reference":2
      },
      "3":{  
         "image_data":{  
            "votable":true,
            "hashed_filename":"4df10b887f12d65f2f541c99f0dd1ef8"
         },
         "image_reference":3
      }
   }
};

var result = Object.keys(o.images).reduce((acc, key) => {
    acc += (acc ? "_" : "") + o.images[key].image_data.hashed_filename; 
    return acc;
},"")

console.log(result);

Here, you can find out more about Object.keys and Array.reduce

Jyoti Adhikari · Accepted Answer · 2017-12-18 13:52:15Z

0

    var result = "";
    var findByValue = function (o, key) {           
        var p;
        for (p in o) {                
            if (o.hasOwnProperty(p) && typeof o[p] === 'object') {                    
                if (o[p][key])
                {                                           
                    result += o[p][key] + "_";                        
                }
                findByValue(o[p], key);                                       
           }
        }       
    };
    findByValue(_data, "hashed_filename");
    console.log(result.substring(0, result.length -1));

answered Dec 18, 2017 at 13:52

Jyoti Adhikari

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