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Javascript Self – Recursive loop | Find within Filter | Loop Within Same Array

October 6, 2022

I have an array with objects:

[
    {
      id:1,
      parent:null,
      value1:22,
      value2:33
    },
    {
      id:2,
      parent:1,
      value1:0,
      value2:0
    },
    {
      id:3,
      parent:1,
      value1:40,
      value2:70
    },
    {
      id:4,
      parent:2,
      value1:40,
      value2:70
    },
    {
      id:5,
      parent:null,
      value1:40,
      value2:70
    }
]

I want to filter all the elements from array whose parent is present in same array in form of id.
Eg. id 1 and 5 should not present since they have null parent and null id is not there in array.

I tried –

array.filter( (item: IItem)=>{
   item.parent == item.id
});

This isnt filtering anything. Getting empty output.
I expect output to be all elements except 1 and 5.

>Solution :

Just to an Array.filter

const data = [
  { id: 1, parent: null, value1: 22, value2: 33 },
  { id: 2, parent: 1, value1: 0, value2: 0 },
  { id: 3, parent: 1, value1: 40, value2: 70 },
  { id: 4, parent: 2, value1: 40, value2: 70 },
  { id: 5, parent: null, value1: 40, value2: 70 },
];
const output = data.filter((node) =>
  data.find((item) => node.parent && item.id === node.parent)
);
console.log(output);