Reduce Entries: Array Utility Function

June 5, 2023

2 min read

If you've ever needed to break an object into its entries via JavaScript's Object.entries function, you'll sometimes need to put it back together again. I've needed this often enough that I encapsulated this functionality into a little utility function called reduceEntries.

#Source

function reduceEntries(entries) {
  return entries.reduce(
    (object, [key, value]) => ({
      ...object,
      [key]: value,
    }),
    {}
  );
}

#Example Usage

Here's a contrived example usage. There are more efficient ways to accomplish the example I've used below. 🤷‍♀️

// We have an object and we want to increment
// the value of every property on the object.
const object = {
  key1: 3,
  key2: 4,
  key3: 5,
};

// Convert all properties on the object to entries
// so we can iterate over them.
const objectEntries = Object.entries(object);

// Increment each entry's value by 1.
const incrementedEntries = objectEntries.map(([key, value]) => [
  key,
  value + 1,
]);

// Rebuild the object
const incrementedObject = reduceEntries(incrementedEntries);

// What incrementedObject looks like now
// {
// 	key1: 4,
// 	key2: 5,
//	key3: 6
// }