isolate key value pairs in array of objects that have null value [duplicate]

Question

I'm trying to create a new object that contains all of the key/value pairs from an object where the values are null. Here is the code thus far -

    const d = { pp: 1700, no: 2300, co: null, ng: 4550, zx: null };
    const nulls = {};

    Object.entries(d).forEach(([k, v]) => v === null ? nulls[k]: v);
    console.log(nulls);

The desired outcome is that the nulls object contains { co: null, zx: null }; however, the code above causes nulls to be an empty object.

What needs to be modified to get the necessary output? Maybe there is a more concise approach...possibly using .filter()?

Object.fromEntries(Object.entries(d).filter(([,v]) => v === null));. But in your forEach you're just failing to assign to the k. v === null && nulls[k] = v); — pilchard
– pilchard, Commented Jul 28, 2022 at 11:32

cmgchess · Accepted Answer · 2022-07-28 11:37:44Z

2

As you have mentioned filter is a possible approach and after that convert back to an object using Object.fromEntries

const d = { pp: 1700, no: 2300, co: null, ng: 4550, zx: null };


const res = Object.fromEntries(Object.entries(d).filter(([k,v]) => v===null))
console.log(res)

possible solution using reduce

 const d = { pp: 1700, no: 2300, co: null, ng: 4550, zx: null };


 const res = Object.entries(d).reduce((acc,[k,v])=> {
  if(v===null)acc[k]=v
  return acc
 },{})
 
 console.log(res)

edited Jul 28, 2022 at 11:37

answered Jul 28, 2022 at 11:33

cmgchess

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5 Comments

knot22 Over a year ago

@pilchard I'm curious how reduce could be used to convert it back to an object. Would you like to post an answer which demonstrates that?

Andreas Over a year ago

This type of question has been asked multiple times on SO. Please close these questions as duplicate instead of adding yet another copy of an already written answer...

knot22 Over a year ago

I had difficulty finding a similar question; thus the post. Do you have a specific link to a post that is essentially the same as this question?

Andreas Over a year ago

@knot22 The dupe target which I've used to close the question... o.O

knot22 Over a year ago

Apologies. I did not understand what was meant by "dupe target" when I read your comment under my original post. Your comment immediately above adds the missing context to understand what that meant.

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