Count the number of threads on a parent comment in ReactJS

Question

I have an array in React like this.

{  
"comments":[  
{  
  "id":1,
  "comment_text":"asdasdadasds",
  "author":"adsfas",
  "post_id":1,
  "children":[]
},
{  
  "id":2,
  "comment_text":"idlsfgh",
  "author":"asdsda",
  "post_id":1,
  "children":[  
    {  
      "id":3,
      "comment_text":"fdsfdsfdsf",
      "author":"sdfdsf",
      "post_id":1,
      "children":[  
        {  
          "id":4,
          "comment_text":"fdsfdsfd",
          "author":"sdfsdfdsfsd",
          "post_id":1,
          "children":[]
        }
      ]
    }
   ]
  }
 ]
}

Now, I want to count the total number of replies on every parent comment. So the array output -

{
 "result":[0, 2]
}

I am using Mongo, Express, React, NodeJS. I have tried of lot of things like using map in React but I am not able to figure out how to do it properly. Can you help me with this.

Answer 1

You can do that using recursion.

• Create a function getCount which takes object and count(previous count) as argument.
• Check if the given object to that function doesn't have children then return 0
• Otherwise call the function recursively on all the children and return count of that child whose count is max using Math.max(). Also add 1 to result which will be count of parent.
• Finally use map() on obj.comments the call getCount on each of element with count=0

const obj = { "comments":[ { "id":1, "comment_text":"asdasdadasds", "author":"adsfas", "post_id":1, "children":[] }, { "id":2, "comment_text":"idlsfgh", "author":"asdsda", "post_id":1, "children":[ { "id":3, "comment_text":"fdsfdsfdsf", "author":"sdfdsf", "post_id":1, "children":[ { "id":4, "comment_text":"fdsfdsfd", "author":"sdfsdfdsfsd", "post_id":1, "children":[] } ] } ] } ] }

let res = obj.comments.map(x => getCount(x));

function getCount(obj,count=0){
  if(!obj.children.length) return 0;
  return Math.max(...obj.children.map(x => getCount(x)+1))
}
console.log(res)