Check if object value exists within a JavaScript array of objects and if not add a new object to array

javascript

functional-programming

javascript-optimization

best-practices

byAlex Kataev·Feb 1, 2025

You can use some() to detect if a value exists by its key in an array:

!array.some(obj => obj.key === newObject.key) && array.push(newObject);

In simple words, this code chunk checks the newObject.key. If it's not found in the array, the newObject gets added to it.

Enhancing code efficiency with functions

Functional encapsulation prevents code duplication and enhances readability and maintainability. It's like packing your suitcase for a trip, where each function is a neatly folded item, ready for use.

Test for existence before adding a new object:

function existsInArray(array, key, value) {
  // Because why bother searching if you've already found it? Efficiency, my friend!
  return array.some(obj => obj[key] === value);
}

Adding a new object to the array:

function addObjectToArray(array, newObject) {
  if (!existsInArray(array, 'key', newObject.key)) {
    array.push(newObject);
    // New member added, let's throw a party 🎉 !
  } else {
    // Oops! They're already on the list. Maybe they just love parties! 🥳
    throw new Error('Object with the given key already exists!');
  }
}

Unique Identifiers: Being special in the array world

Identifiers, much like our fingerprints, should be unique. When adding objects, you can generate unique IDs by taking the length of your array:

function generateId(array) {
  // +1 because no one wants to be a zero 🦸
  return array.length + 1;
}

newObject.id = generateId(array);

Watch out, though! This method might lead to collisions. Consider employing a UUID generator or a more robust ID-creation strategy! 💥

Clean Code Using Modern JavaScript

Embrace modern JavaScript syntax for improved readability. Leverage destructuring to unpack properties from objects:

const addIfNotExist = ({ array, newObject, keyField = 'key' }) => {
  const { [keyField]: keyValue } = newObject;
  if (!existsInArray(array, keyField, keyValue)) array.push(newObject);
  // The array gang just got a new member, yay!
};

With reusable functions and clear parameter names, even a JavaScript newbie can understand what's going on! 🥳

Juggling edge cases and concurrency

Nobody likes a party pooper, but you can't ignore edge cases like identical usernames or concurrent updates that could crash your code party!

Always be prepared to handle these party spoilers gracefully:

...
if (existsInArray(array, 'username', newObject.username)) {
  // Uh-oh! Same usernames? This party just got interesting 🕵️‍♀️
  // Handling logic for duplicate usernames goes here
}
...