Htykuut

I have a set of data I'm collecting that outputs something like this:

[

    {

        hostName: 'server1',

        service: 'service1',

        perfData: 'unique string5',

        state: 1

    },

    {

        hostName: 'server1',

        service: 'service2',

        perfData: 'unique string4',

        state: 1

    },

    {

        hostName: 'server1',

        service: 'service3',

        perfData: 'unique string3',

        state: 1

    },

    {

        hostName: 'server2',

        service: 'service1',

        perfData: 'unique string2',

        state: 1

    },

    {

        hostName: 'server2',

        service: 'service2',

        perfData: 'unique string1',

        state: 1

    }

]

I'm trying to loop through this array of objects with javascript to output the following:

let desiredOutput = [{'server1': [{

        service: 'service1',

        perfData: 'unique string1',

        state: 1

        },

        {

        service: 'service2',

        perfData: 'unique string1',

        state: 1

        },

        {

        service: 'service3',

        perfData: 'unique string1',

        state: 1

        }],

    'server2': {

        service: 'service1',

        perfData: 'unique string1',

        state: 1

    }

}];

Does Javascript have something similar to dict comprehension? Not sure how to loop through an array of objects and merge them and make them an object with an array of objects. In python I could use something like this:

raw_data = [{'hostName': 'server1', 'serviceName': 'service1'}, {'hostName': 'server1', 'serviceName': 'service2'}, {'hostName': 'server1', 'serviceName': 'service3'}, {'hostName': 'server2', 'serviceName': 'service1'}, {'hostName': 'server2', 'serviceName': 'service2'}]

services = defaultdict(list)

for service in raw_data:

    host_name = service.get('hostName')

    service_name = service.get('service')

    new_dict = {'hostName': host_name, 'serviceName': service_name}

    services[new_dict['hostName']].append(new_dict)

print(services)

I found something close with this Merge javascript objects in array with same key but not quite what I'm looking for.

Not sure about dict comprehensions (you're not using them in your snippet), but defaultdict could be done quite easily:

class DefaultMap extends Map {



    constructor(fn, entries = ) {

        super(entries);

        this.fn = fn;

    }



    get(key) {

        if (!this.has(key))

            this.set(key, this.fn());

        return super.get(key)

    }

}



services = new DefaultMap(Array)



for (let service of raw_data)

    services.get(service.hostName).push(service)

Unfortunately, JS doesn't come with "batteries included", so you have to code stuff like that from scratch or look around for a library.

Your output structure is a bit strange (an array of one element?). Using reduce is a reasonable approach, building arrays for each unique key:

const data = [ { hostName: 'server1', service: 'service1', perfData: 'unique string5', state: 1 }, { hostName: 'server1', service: 'service2', perfData: 'unique string4', state: 1 }, { hostName: 'server1', service: 'service3', perfData: 'unique string3', state: 1 }, { hostName: 'server2', service: 'service1', perfData: 'unique string2', state: 1 }, { hostName: 'server2', service: 'service2', perfData: 'unique string1', state: 1 } ];



console.log([data.reduce((a, e) => {

  const name = e.hostName;

  delete e.hostName;

  a[name] = name in a ? a[name].push(e) && a[name] : [e];

  return a;

}, {})]);