CODEWITHSUNDEEP
javascriptnode.jsmongoose
Prithviraj Mitra
Prithviraj Mitra

Reputation: 11812

read array in javascript

I am new in javascript and using nodejs and mongoose query to get a result which I would like to loop through and get some values in another array.

The resultset looks like 

[ { _id: 5366e9049cfc825b32966852,
 companies:
     [ 5ab20bb69cb2754e949a09dc,
       5ac5d53983d45353bc6a9c54,
       5ac62eeca5421e4cb9abf63e]
},
{ _id: 5b9251f8ae8db624755f4b90,
 companies:
     [ 5b461c892bb9c81bd3ed4a25,
       5b5086196947782fbc873d28,
       5b76a6c79dc71a4a12564cc5 ]
}]

The final array should look like --

 [ 5ab20bb69cb2754e949a09dc,
   5ac5d53983d45353bc6a9c54,
   5ac62eeca5421e4cb9abf63e,
   5b461c892bb9c81bd3ed4a25,
   5b5086196947782fbc873d28,
   5b76a6c79dc71a4a12564cc5]

My code--

    Model.find().exec(function(err,gdoc){
          if(err)
          {
             callback({err:err,message:"Error looking up company"});
          }else
          {
             for (var i = 0, len = gdoc.length; i < len; i++) {                    
                    console.log(gdoc.companies);
              }
          }
    });

I am getting undefined values.

Any help is highly appreciated. Thanks in advance.

Upvotes: 0

Views: 2387

Answers (7)

LKing
LKing

Reputation: 49

const data = [ { _id: '5366e9049cfc825b32966852',
 companies:
     [ '5ab20bb69cb2754e949a09dc',
       '5ac5d53983d45353bc6a9c54',
       '5ac62eeca5421e4cb9abf63e']
},
{ _id: '5b9251f8ae8db624755f4b90',
 companies:
     [ '5b461c892bb9c81bd3ed4a25',
       '5b5086196947782fbc873d28',
       '5b76a6c79dc71a4a12564cc5' ]
}]
let outputArr = []
data.map(d => outputArr.push(d.companies));
//Flatten
console.log([].concat.apply([],outputArr))

Both flatMap and flat which are currently an 'experimental technology' will allow a cleaner approach to this problem in the future. See:

Array.prototype.flat(): https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat

Array.prototype.flatMap(): https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flatMap

Upvotes: 0

str
str

Reputation: 44969

The reason why you are getting undefined is that you try to access the non-existing companies property on gdoc. Instead of gdoc.companies, you have to use gdoc[i].companies.

Instead of your loop, you can use Array.prototype.concat together with the spread syntax (...) and Array.prototype.map as follows:

const gdoc = [
  {
    _id: '5366e9049cfc825b32966852',
    companies: [
      '5ab20bb69cb2754e949a09dc',
      '5ac5d53983d45353bc6a9c54',
      '5ac62eeca5421e4cb9abf63e',
    ],
  },
  {
    _id: '5b9251f8ae8db624755f4b90',
    companies: [
      '5b461c892bb9c81bd3ed4a25',
      '5b5086196947782fbc873d28',
      '5b76a6c79dc71a4a12564cc5',
    ],
  },
];

const companies = [].concat(...gdoc.map(doc => doc.companies));
console.log(companies);

Upvotes: 2

Jos&#233; Alves Durand Neto
Jos&#233; Alves Durand Neto

Reputation: 62

You can do some thing like that!

var docs= [ { _id: "5366e9049cfc825b32966852",
 companies:
     [ "5ab20bb69cb2754e949a09dc",
       "5ac5d53983d45353bc6a9c54",
       "5ac62eeca5421e4cb9abf63e"]
},
{ _id: "5b9251f8ae8db624755f4b90",
 companies:
     [ "5b461c892bb9c81bd3ed4a25",
       "5b5086196947782fbc873d28",
       "5b76a6c79dc71a4a12564cc5" ]
}];
// your companies will be put in the folowing variable
var companies = [];

for ( var doc of docs){
    for (var item of doc.companies){
        companies.push(item)
    }
}

console.log(companies)

Upvotes: 0

phuzi
phuzi

Reputation: 13060

How about running a reduce over the array.

const model = [{
    _id: "5366e9049cfc825b32966852",
    companies: [
      "5ab20bb69cb2754e949a09dc",
      "5ac5d53983d45353bc6a9c54",
      "5ac62eeca5421e4cb9abf63e"
    ]
  },
  {
    _id: "5b9251f8ae8db624755f4b90",
    companies: [
      "5b461c892bb9c81bd3ed4a25",
      "5b5086196947782fbc873d28",
      "5b76a6c79dc71a4a12564cc5"
    ]
  }
];

const reducer = (acc, value) => {
  acc.push(...value.companies);
  return acc;
};

console.log(model.reduce(reducer, []));

Upvotes: 0

Adrian
Adrian

Reputation: 8597

You can use the following method:

const map = [...[].concat(...arr.map((o) => o.companies))]

var arr = [ { _id: "5366e9049cfc825b32966852",
 companies:
     [ "5ab20bb69cb2754e949a09dc",
       "5ac5d53983d45353bc6a9c54",
       "5ac62eeca5421e4cb9abf63e"]
},
{ _id: "5b9251f8ae8db624755f4b90",
 companies:
     [ "5b461c892bb9c81bd3ed4a25",
       "5b5086196947782fbc873d28",
       "5b76a6c79dc71a4a12564cc5" ]
}];


const map = [...[].concat(...arr.map((o) => o.companies))]

console.log(map);

Upvotes: 0

Shilly
Shilly

Reputation: 8589

Basically you're trying to concatenate all the company fields of the results array. As long as you know that the key is companies, this is an easy reduction.

Arrays have a couple of builtin methods that make transforming them very easy, compared to having to use a for-loop.

Array.forEach(), Array.map(), Array.reduce() and Array.find() are the most frequently used ones.

//  Since these id's contain letters as well, they need to be strings.
const data = [
  {
    _id: "5366e9049cfc825b32966852",
    companies:[
      "5ab20bb69cb2754e949a09dc",
      "5ac5d53983d45353bc6a9c54",
      "5ac62eeca5421e4cb9abf63e"
    ]
  },
  {
    _id: "5b9251f8ae8db624755f4b90",
   companies:[
    "5b461c892bb9c81bd3ed4a25",
    "5b5086196947782fbc873d28",
    "5b76a6c79dc71a4a12564cc5"
    ]
  }
];

const companies = data.reduce(( result, item ) => result.concat( item.companies ), []);

console.log( companies );

Upvotes: 0

mankowitz
mankowitz

Reputation: 2031

You want something like this:

var k = [{
    _id: "5366e9049cfc825b32966852",
    companies: ["5ab20bb69cb2754e949a09dc",
      "5ac5d53983d45353bc6a9c54",
      "5ac62eeca5421e4cb9abf63e"
    ]
  },
  {
    _id: "5b9251f8ae8db624755f4b90",
    companies: ["5b461c892bb9c81bd3ed4a25",
      "5b5086196947782fbc873d28",
      "5b76a6c79dc71a4a12564cc5"
    ]
  }
];

var res = [];
k.forEach(function(id) {
  res.push(...id.companies)
});


console.log(res);

Upvotes: -1

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