How to create an array with some properties from an inner JSON array in javascript

Question

So I have :

list = 
    {
      id: 1,
      arr: [
        {index : 1 , description: "lol" , author: "Arthur"},
        {index : 2 , description: "sdadsa" , author: "Bob"},
        {index : 3 , description: "loasd" , author: "Mackenzie"}
      ]
    }

and I want to create an array only with description and author property from the arr array.

I tried var a = {l : list.arr.map(x => {x.description,x.author})}. But all items from the array are undefined .

The arr in your list is not array, are you sure no typo here? — ikhvjs
– ikhvjs, Commented Jul 19, 2021 at 6:43
Thank you, i edited the question. This is a simplified version of what I'm trying to do. — radurbalau
– radurbalau, Commented Jul 19, 2021 at 6:45

StackByMe · Accepted Answer · 2021-07-19 06:51:00Z

4

Another approach would be to use the rest parameter. This way you can remove the index and keep everything else intact.

var list = {
  id: 1,
  arr: [
    { index: 1, description: "lol", author: "Arthur" },
    { index: 2, description: "sdadsa", author: "Bob" },
    { index: 3, description: "loasd", author: "Mackenzie" },
  ],
};

var a = list.arr.map(({index, ...rest}) => rest);

console.log(a);

answered Jul 19, 2021 at 6:51

StackByMe

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1 Comment

Rush W. Over a year ago

Wow, this was great! Amazing thought!

ikhvjs · Accepted Answer · 2021-07-19 06:47:04Z

1

You almost finish, you should define the key in your return object in the map funciton.

var list = {
  id: 1,
  arr: [
    { index: 1, description: "lol", author: "Arthur" },
    { index: 2, description: "sdadsa", author: "Bob" },
    { index: 3, description: "loasd", author: "Mackenzie" },
  ],
};

var a = list.arr.map(x => ({
  description: x.description,
  author: x.author,
}));

console.log(a);

answered Jul 19, 2021 at 6:47

ikhvjs

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2 Comments

radurbalau Over a year ago

So the mistake was that i didnt had ( ) wrapped to the object when I was returning in map ?

ikhvjs Over a year ago

@radurbalau, yes. Also, you should define the key for the object too.

Rush W. · Accepted Answer · 2021-07-19 06:48:09Z

1

list = {
  id: 1,
  arr: [{
      index: 1,
      description: "lol",
      author: "Arthur"
    },
    {
      index: 2,
      description: "sdadsa",
      author: "Bob"
    },
    {
      index: 3,
      description: "loasd",
      author: "Mackenzie"
    }
  ]
}

var a = {
  l: list.arr.map(x => ({
    "description": x.description,
    "author": x.author
  }))
}
console.log(a);

answered Jul 19, 2021 at 6:48

Rush W.

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Comments

Danial · Accepted Answer · 2021-07-19 06:54:25Z

1

You just forget to define keys in return object.

var list = {
  id: 1,
  arr: [
    { index: 1, description: "lol", author: "Arthur" },
    { index: 2, description: "sdadsa", author: "Bob" },
    { index: 3, description: "loasd", author: "Mackenzie" },
  ],
};

var a = l.arr.map(x => ({
  description: x.description,
  author: x.author,
}));

answered Jul 19, 2021 at 6:54

Danial

1,6432 gold badges17 silver badges26 bronze badges

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