delete object from a nested object in javascript

Question

I have a nested object of this structure.

mainObject: {
   1: {
         id: 1,
         name:'alpha'
      },
   2: {
         id: 2,
         name:'beta'
      },
   3: {
         id: 3,
         name:'gamma'
        
      }
}

i want to delete on object from this ,say 1 but that in an immutable way . I tried the following code.

    const list =Object.values(mainObject)
    const newList=list.filter((item)=>{item.id!=1})
    newList.forEach((item)=>{
        mainObject[item.id]={
          id: item.id,
          name:item.name
        }
    })

this is not working .What am i doing wrong. Thanks in advance.

Are you wanting to remove the object with the id of 1, or the object at key 1? — Nick Parsons
– Nick Parsons, Commented Sep 12, 2020 at 3:38
explain what you mean by immutability in this context - by the way const newList=list.filter((item)=>{item.id!=1}) will ALWAYS be an empty list since your callback doesn't return anything — Jaromanda X
– Jaromanda X, Commented Sep 12, 2020 at 3:39

hgb123 · Accepted Answer · 2020-09-12 03:55:16Z

You could use destruct assignment for deletion

const { 1: _, ...newObject } = mainObject

const mainObject = {
  1: {
    id: 1,
    name: "alpha",
  },
  2: {
    id: 2,
    name: "beta",
  },
  3: {
    id: 3,
    name: "gamma",
  },
}

const { 1: _, ...newObject } = mainObject

console.log(mainObject)
console.log(newObject)

Or clone mainObject in to an different object then apply deletion

const newObject = { ...mainObject }
delete newObject[1]

const mainObject = {
  1: {
    id: 1,
    name: "alpha",
  },
  2: {
    id: 2,
    name: "beta",
  },
  3: {
    id: 3,
    name: "gamma",
  },
}

const newObject = { ...mainObject }
delete newObject[1]

console.log(mainObject)
console.log(newObject)

Or transform object into array of key-value pairs, reject your delete pair and then transform it back to object

const newObject = Object.fromEntries(
  Object.entries(mainObject).filter(([key]) => key !== "1")
)

const mainObject = {
  1: {
    id: 1,
    name: "alpha",
  },
  2: {
    id: 2,
    name: "beta",
  },
  3: {
    id: 3,
    name: "gamma",
  },
}

const newObject = Object.fromEntries(
  Object.entries(mainObject).filter(([key]) => key !== "1")
)

console.log(mainObject)
console.log(newObject)

Reference

Destructuring assignment

Spread operator (...)

Object.prototype.entries()

Object.prototype.fromEntries()

yes my key is a number so in side newObject i need it as a number @hgb123

Rokibul Islam · Accepted Answer · 2020-09-12 04:11:49Z

You can use delete operator and spread syntax to achieve what you want. For the object you have mentioned, let me walk you through it.

const mainObject = {
  1: {
    id: 1,
    name: 'alpha',
  },
  2: {
    id: 2,
    name: 'beta',
  },
  3: {
    id: 3,
    name: 'gamma',
  },
};

const newObj = { ...mainObject};
delete newObj["1"];

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