CODEWITHSUNDEEP
javascript
Min UD
Min UD

Reputation: 99

getting the length of the array of objects inside an object

I would like to map the object and get the number/length of replies that can be found in replies in this case 2. I have fetched this data from the API and is unable to get the number of replies that can be found here.


let data = [ 
   { 
      "feedbackId":32,
      "sender":"12345"
      "comment":"Test Comment",
      "replies":[ 
         { 
            "feedbackLogId":32,
            "feedbackReplyLogId":1,
            "comments":"So this is 1",
            "createdBy":"Jack",
         },
         { 
            "feedbackLogId":32,
            "feedbackReplyLogId":2,
            "comments":"2nd one",
            "createdBy":"Min",
         }
      ],
   }
]

This is what I've done. I am only able to get 1 as the length.

let repliesToRender = data.map((item) => {item.replies})
let numReplies = repliesToRender.length

Upvotes: 0

Views: 73

Answers (4)

Tushar Vaghela
Tushar Vaghela

Reputation: 1243

Another approach. This will run faster in case of large data-sets, as it's not using loops.

let data = [ 
   { 
      "feedbackId":32,
      "sender":"12345",
      "comment":"Test Comment",
      "replies":[ 
         { 
            "feedbackLogId":32,
            "feedbackReplyLogId":1,
            "comments":"So this is 1",
            "createdBy":"Jack",
         },
         { 
            "feedbackLogId":32,
            "feedbackReplyLogId":2,
            "comments":"2nd one",
            "createdBy":"Min",
         }
      ],
   }
]

let {replies} = data[0];
console.log(replies.length);

Upvotes: 0

Sasi Kumar M
Sasi Kumar M

Reputation: 2630

If replies count is needed for each of the objects, then below will return array of replies count for respective objects in order,

let eachObjectsRepliesCount = data.map(({replies}) => replies.length);

If replies count is needed for all the objects combined, then below will return the total replies count,

let repliesToRender = data.map((item) => item.replies)
let totalRepliesCount = repliesToRender[0].length

Upvotes: 0

arizafar
arizafar

Reputation: 3132

You can calculate reply per feedback using Array.prototype.map

for calculting total number of replies you can use Array.prototype.reduce

let data = [{"feedbackId":32,"sender":"12345","comment":"Test Comment","replies":[{"feedbackLogId":32,"feedbackReplyLogId":1,"comments":"So this is 1","createdBy":"Jack"},{"feedbackLogId":32,"feedbackReplyLogId":2,"comments":"2nd one","createdBy":"Min"}]},{"feedbackId":32,"sender":"12345","comment":"Test Comment","replies":[{"feedbackLogId":32,"feedbackReplyLogId":1,"comments":"So this is 1","createdBy":"Jack"},{"feedbackLogId":32,"feedbackReplyLogId":2,"comments":"2nd one","createdBy":"Min"}]}]

let repliesCount = data.map(({replies}) => replies.length);
console.log('per replies',repliesCount);

let totalCount = data.reduce((a,c) => a + c.replies.length, 0);
console.log('total replies ',totalCount)

Upvotes: 1

Code Maniac
Code Maniac

Reputation: 37775

You have 2 issue in your code,

let repliesToRender = data.map((item) => {item.replies})

should be

let repliesToRender = data.map((item) => item.replies)

And map return you array so your repliesToRender will be an array of array so you need

let numReplies = repliesToRender[0].length

Or just 

let numReplies = data.replies.length


let data = [ 
   { 
      "feedbackId":32,
      "sender":"12345",
      "comment":"Test Comment",
      "replies":[ 
         { 
            "feedbackLogId":32,
            "feedbackReplyLogId":1,
            "comments":"So this is 1",
            "createdBy":"Jack",
         },
         { 
            "feedbackLogId":32,
            "feedbackReplyLogId":2,
            "comments":"2nd one",
            "createdBy":"Min",
         }
      ],
   }
]


let repliesToRender = data.map((item) => item.replies)
let numReplies = repliesToRender[0].length
console.log(numReplies)

Upvotes: 1

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