Subset Json object in Javascript

Question

Given an array of json object like this below, (the json object such as "name2" and "name4" will definitely have only one key-value)

[
  {
    abc: 123,
    id: '18263322',
    name: 'name1'
  },
  { name: 'name2' },
  {
    abc: 456,
    id: '18421634',
    name: 'name3'
  },
  { name: 'name4' }
]

How can I subset this so that I have two array of json objects:

[
  {
    abc: 123,
    id: '18263322',
    name: 'name1'
  },
  {
    abc: 456,
    id: '18421634',
    name: 'name3'
  }
]

and

[
  { name: 'name2' },
  { name: 'name4' }
]

What do you want exactly? Can you explain more your question? Thank — segandiaye
– segandiaye, Commented Jul 19, 2021 at 0:05
I would like to split the first array (in the first code section) in to two array of json. I use this code: data = [ { abc: 123, id: '18263322', name: 'name1' }, { name: 'name2' }, { abc: 456, id: '18421634', name: 'name3' }, { name: 'name4' } ] data.filter(function(x) { console.log(Object.keys(x).length !== 1); }); This gets me true and false but not the array itself, and it seems very slow to process — Sun Tianyi
– Sun Tianyi, Commented Jul 19, 2021 at 0:12
@SunTianyi Since you have tried so you should include it in the question itself. So that other people can understand what have you tried — DecPK
– DecPK, Commented Jul 19, 2021 at 0:16

DecPK · Accepted Answer · 2021-07-19 00:19:09Z

1

You can use reduce here

const arr = [
  {
    abc: 123,
    id: "18263322",
    name: "name1",
  },
  { name: "name2" },
  {
    abc: 456,
    id: "18421634",
    name: "name3",
  },
  { name: "name4" },
];

const [single, multiple] = arr.reduce((acc, curr) => {
    Object.keys(curr).length === 1 ? acc[0].push(curr) : acc[1].push(curr);
    return acc;
  },[[], []]
);

console.log(single);
console.log(multiple);

You can also do something like

const [single, multiple] = arr.reduce((acc, curr) => {
    acc[Object.keys(curr).length === 1 ? 0 : 1].push(curr);
    return acc;
  },[[], []]);

using filter

const arr = [
  {
    abc: 123,
    id: "18263322",
    name: "name1",
  },
  { name: "name2" },
  {
    abc: 456,
    id: "18421634",
    name: "name3",
  },
  { name: "name4" },
];

const single = arr.filter((o) => Object.keys(o).length === 1);
const multiple = arr.filter((o) => Object.keys(o).length !== 1);

console.log(single);
console.log(multiple);

edited Jul 19, 2021 at 0:19

answered Jul 19, 2021 at 0:14

DecPK

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5 Comments

Sun Tianyi Over a year ago

That works like a charm! I thought about Object.keys(x).length but never thought about reduce. Thank you so much!

DecPK Over a year ago

@SunTianyi Added solution with filter also. Have a look

Sun Tianyi Over a year ago

Do you mind commenting on which one is more efficient? I think the reduce is more efficient because it seems like only looping through once? whereas the second method does two filters loops @decpk

DecPK Over a year ago

You shouldn't consider the efficient solution if the dataset is small. If it would have millions of records then I would go with reduce since it takes a single loop to filter the data.

Sun Tianyi Over a year ago

Thanks for your advise! I was asking the efficiency because I have maybe ten thousands of records.

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