There is a condition where i need to convert Array of objects into Array of Arrays

Question

There is a condition where i need to convert Array of objects into Array of Arrays. An array is given below as data convert this array as formatedArray.

data = [
      {
        "total": 1,
        "third": 0,
        "city": "Agra",
        "first": 0,
        "second": 0
      },
      {
        "total": 2,
        "third": 0,
        "city": "Agra",
        "first": 0,
        "second": 0
      },
      {
        "total": 3,
        "third": 0,
        "city": "Delhi",
        "first": 0,
        "second": 0
      },
      {
        "total": 4,
        "third": 0,
        "city": "Delhi",
        "first": 0,
        "second": 0
      }
]

How can I convert the array of objects above into an array of arrays below?

formatedArray=[
  "Agra":[
    {
      "total": 1,
      "third": 0,
      "city": "Agra",
      "first": 0,
      "second": 0
    },
    {
      "total": 2,
      "third": 0,
      "city": "Agra",
      "first": 0,
      "second": 0
    }
  ],
  "Delhi":[
    {
      "total": 4,
      "third": 0,
      "city": "Delhi",
      "first": 0,
      "second": 0
    },
    {
      "total": 4,
      "third": 0,
      "city": "Delhi",
      "first": 0,
      "second": 0
    }
  ]
]

just aggregate elems of your array by city: take a map, check if map has the city, if yes use the value to push the element, otherwise adds an empty city to the map and push it your elem — grodzi
– grodzi, Commented Oct 15, 2019 at 11:19
This is not an Array, it looks like a Json (Java). You don't state the language — Ioannis Barakos
– Ioannis Barakos, Commented Oct 15, 2019 at 11:36
What language are you using? ( Edit your post and include the corresponding tag next to arrays. ) — ryyker
– ryyker, Commented Oct 15, 2019 at 11:39

StepUp · Accepted Answer · 2019-10-15 13:48:23Z

2

You can do it through vanilla JavaScript. The method which can be used is reduce() method:

const data = [
    {
      "total": 1,
      "third": 0,
      "city": "Agra",
      "first": 0,
      "second": 0
    },
    {
      "total": 2,
      "third": 0,
      "city": "Agra",
      "first": 0,
      "second": 0
    },
    {
      "total": 3,
      "third": 0,
      "city": "Delhi",
      "first": 0,
      "second": 0
    },
    {
      "total": 4,
      "third": 0,
      "city": "Delhi",
      "first": 0,
      "second": 0
    }
];

and the code looks like this:

const desired = data.reduce((acc, currentValue) => {
    acc[currentValue.city] = acc[currentValue.city] || [];        
    acc[currentValue.city].push(currentValue);    
    return acc;
}, {})

console.log(desired);

edited Oct 15, 2019 at 13:48

answered Oct 15, 2019 at 12:34

StepUp

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2 Comments

grodzi Over a year ago

You don't need the if: (acc[currentValue.city] exists from previous line) @StepUp

StepUp Over a year ago

@user753642 you are right! It is great catch! Thanks for so great comment! :)

user12213283 · Accepted Answer · 2019-10-15 11:36:22Z

1

I suggesty you taking a look at the lodash groupby function:

https://lodash.com/docs/4.17.15#groupBy

formatedArray = _.groupBy(data, obj => obj.city);

Here is a quick stackblitz-example based on angular

https://stackblitz.com/edit/angular-dpj8jh

answered Oct 15, 2019 at 11:36

user12213283

1 Comment

user12213283 Over a year ago

perfect! Glad it solved your problem. Would you mind accepting my answer as correct? Greetings

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