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Revert an object with Javascript

Problem

Let’s say you have a javascript object like:

const countryCodes = {
  'United States': 'US',
  'Canada': 'CA',
  'Mexico': 'MX',
};

And you want to invert the keys and values to get the reverse object:

const codeCountries = {
  'US': 'United States',
  'CA': 'Canada',
  'MX': 'Mexico'
};

Solution

Here’s a simple function to do that:

function revertObject(obj) {
  return Object.fromEntries(
    Object.entries(obj).map(a => a.reverse())
  )
}

Explanation

How it works:

  • The Object.entries(obj) method converts the object into an array of key-value pairs
[["United States","US"],["Canada","CA"],["Mexico","MX"]]
  • The map(a => a.reverse()) function then reverses each key-value pair
[["US","United States"],["CA","Canada"],["MX","Mexico"]]
  • Object.fromEntries() converts the array of reversed pairs back into an object
{
  'US': 'United States',
  'CA': 'Canada',
  'MX': 'Mexico'
};