JavaScript - adding extra keys values to an object using spread operation or alternative approaches

Question

Here is the code:

    let bucket = [[],[],[],[],[],[],[],[],[],[]];

    bucket = {...Object.keys(bucket)
                       .sort((a,b) => b-a)
                       .filter(key => key > 0)
                       .map(key => '-'+key), 
              ...bucket};

   console.log(bucket);

Problem: the first line of code is not adding the negative keys of the original bucket object into the object, with all properties (keys) having empty arrays as their corresponding value.

Bucket only shows its original properties and values after this line of code is evaluated

How can I get this to work?

Ori Drori · Accepted Answer · 2021-09-20 11:52:03Z

1

The Array.map() creates an array of strings with your negative keys, and they are overwritten when you spread the bucket array. Instead create pairs of [new key, []] convert to an object with Object.fromEntries(), and then spread them:

const bucket = [[],[],[],[],[],[],[],[],[],[]];

const result = {
  ...Object.fromEntries(
    Object.keys(bucket)
      .filter(key => key > 0)
      .sort((a, b) => b-a)
      .map(key => [-key, []])
  ),
  ...bucket};

console.log(result);

answered Sep 20, 2021 at 11:52

Ori Drori

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1 Comment

Vahe Over a year ago

Ok... I see now, so my array needs to be converted back to an object and then be spread out which I did not successfully do. I have now a new method I need to use regularly when necessary, the fromEntries method. I also incorrectly did not specify the empty value for key. Can this be done without a pair of array values, but more like bracket of [-key] alone with a corresponding property? Please suggest. Thank you so much.

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