using lodash transform same keys into one and create array of it's values

Question

I would like to transform belo input.json file. I would like to merge all the category key into one and create array of names, if it matches.

I am looking for a solution using only lodash or only JS/ES*

There are similar questions already asked, but most of them involve two different json's. Please shed some light on the solution

[
    {
        "category": "Salman Khan",
        "names": "Bhaijan"
    },
    {
        "category": "Salman Khan",
        "names": "Sallu"
    },
    {
        "category": "Salman Khan",
        "names": "Dabangg Khan"
    },
    {
        "category": "Salman Khan",
        "names": "Sultan"
    },
    {
        "category": "Shahrukh Khan",
        "names": "SRK"
    },
    {
        "category": "Shahrukh Khan",
        "names": "King Khan"
    },
    {
        "category": "Akshay Kumar",
        "names": "Khiladi"
    },
    {
        "category": "Akshay Kumar",
        "names": "Akki"
    },
    {
        "category": "Aamir Khan",
        "names": "A.K."
    },
    {
        "category": "Aamir Khan",
        "names": "Mr. Perfectionist"
    },
    {
        "category": "Priyanka Chopra",
        "names": "Piggy Chops"
    },
    {
        "category": "Kareena Kapoor",
        "names": "Bebo"
    }
]

expected json

[
    {
        "category": "Salman Khan",
        "names": ["Bhaijan", "Sallu", "Dabangg Khan", "Sultan"]
    },
    {
        "category": "Shahrukh Khan",
        "names": ["SRK", "King Khan"]
    },
    {
        "category": "Akshay Kumar",
        "names": ["Khiladi", "Akki", "A.K."]
    },
    {
        "category": "Aamir Khan",
        "names": ["Mr. Perfectionist"]
    },
    {
        "category": "Priyanka Chopra",
        "names": ["Piggy Chops"]
    },
    {
        "category": "Kareena Kapoor",
        "names": ["Bebo"]
    }
]

Suren Srapyan · Accepted Answer · 2018-02-27 10:43:32Z

3

Iterate over the array using Array#reduce function and check if an object already exist with the current item name. If yes, just push the name into it, if not create a new object with the current item name.

const data = [
    {
        "category": "Salman Khan",
        "names": "Bhaijan"
    },
    {
        "category": "Salman Khan",
        "names": "Sallu"
    },
    {
        "category": "Salman Khan",
        "names": "Dabangg Khan"
    },
    {
        "category": "Salman Khan",
        "names": "Sultan"
    },
    {
        "category": "Shahrukh Khan",
        "names": "SRK"
    },
    {
        "category": "Shahrukh Khan",
        "names": "King Khan"
    },
    {
        "category": "Akshay Kumar",
        "names": "Khiladi"
    },
    {
        "category": "Akshay Kumar",
        "names": "Akki"
    },
    {
        "category": "Aamir Khan",
        "names": "A.K."
    },
    {
        "category": "Aamir Khan",
        "names": "Mr. Perfectionist"
    },
    {
        "category": "Priyanka Chopra",
        "names": "Piggy Chops"
    },
    {
        "category": "Kareena Kapoor",
        "names": "Bebo"
    }
]

const arr = data.reduce((acc, item) => {
  
  const found = acc.find(i => i.category === item.category);
  
  if(found) {
     found.names.push(item.names);
  } else {
     acc.push({category: item.category, names: [item.names]})
  }
  
  return acc;
}, []);

console.log(arr);

edited Feb 27, 2018 at 10:43

answered Feb 27, 2018 at 10:27

Suren Srapyan

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2 Comments

Rinav Over a year ago

Thanks for the quick answer, However can you explain what does the last empty parameter do }, []);

Suren Srapyan Over a year ago

It is the signature of the reduce function. I just pass an empty array as a start value for the acc inside it

ryeballar · Accepted Answer · 2018-02-27 12:41:35Z

You can use lodash#groupBy, to group each object in the collection by the category key, and then lodash#map to transform each group into an array format of your liking.

var result = _(data)
  .groupBy('category')
  .map(function(group, category) {
    return {
      category: category,
      names: _.map(group, 'names')
    };
  })
  .value();

var data = [
    {
        "category": "Salman Khan",
        "names": "Bhaijan"
    },
    {
        "category": "Salman Khan",
        "names": "Sallu"
    },
    {
        "category": "Salman Khan",
        "names": "Dabangg Khan"
    },
    {
        "category": "Salman Khan",
        "names": "Sultan"
    },
    {
        "category": "Shahrukh Khan",
        "names": "SRK"
    },
    {
        "category": "Shahrukh Khan",
        "names": "King Khan"
    },
    {
        "category": "Akshay Kumar",
        "names": "Khiladi"
    },
    {
        "category": "Akshay Kumar",
        "names": "Akki"
    },
    {
        "category": "Aamir Khan",
        "names": "A.K."
    },
    {
        "category": "Aamir Khan",
        "names": "Mr. Perfectionist"
    },
    {
        "category": "Priyanka Chopra",
        "names": "Piggy Chops"
    },
    {
        "category": "Kareena Kapoor",
        "names": "Bebo"
    }
];

var result = _(data)
  .groupBy('category')
  .map(function(group, category) {
    return {
      category: category,
      names: _.map(group, 'names')
    };
  })
  .value();

console.log(result);

.as-console-wrapper{min-height:100%;top:0}

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js"></script>

fyasir · Accepted Answer · 2018-02-27 13:19:10Z

Here's the possible solution using reduce method.

const data = [
    {
        "category": "Salman Khan",
        "names": "Bhaijan"
    },
    {
        "category": "Salman Khan",
        "names": "Sallu"
    },
    {
        "category": "Salman Khan",
        "names": "Dabangg Khan"
    },
    {
        "category": "Salman Khan",
        "names": "Sultan"
    },
    {
        "category": "Shahrukh Khan",
        "names": "SRK"
    },
    {
        "category": "Shahrukh Khan",
        "names": "King Khan"
    },
    {
        "category": "Akshay Kumar",
        "names": "Khiladi"
    },
    {
        "category": "Akshay Kumar",
        "names": "Akki"
    },
    {
        "category": "Aamir Khan",
        "names": "A.K."
    },
    {
        "category": "Aamir Khan",
        "names": "Mr. Perfectionist"
    },
    {
        "category": "Priyanka Chopra",
        "names": "Piggy Chops"
    },
    {
        "category": "Kareena Kapoor",
        "names": "Bebo"
    }
];

const resultObject = data.reduce((acc, value) => {
  acc[value.category] = acc[value.category] || [];
  acc[value.category].push(value.names);
  return acc; 
},{});

const results = Object.keys(resultObject).map(key => ({ category: key, names: resultObject[key]}));

console.log(results);

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