How can I perform a deep merge rather than a shallow merge?

Other Questions JavaScript
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1

Standard JavaScript methods like Object.assign and the object spread operator create shallow merges. Consider this issue:

// Flat structure
const obj1 = { key1: 5 };
const obj2 = { key2: 7 };
const mergedObj = { ...obj1, ...obj2 }; // { key1: 5, key2: 7 }

This behaves as expected. However, nesting changes things:

// Nested structure
const obj1 = { key: { inner1: 5 } };
const obj2 = { key: { inner2: 7 } };
const mergedObj = { ...obj1, ...obj2 }; // { key: { inner2: 7 } }

You might expect:

{ key: { inner1: 5, inner2: 7 } }

But the result is:

{ key: { inner2: 7 } }

Because spread syntax merges only one level deep. Is there a method to achieve this? For additional insights into deep merging, refer to the Wikipedia page on Data Merge.

2

Hello there! Interesting challenge you’ve got with merging objects! In JavaScript, achieving a deep merge requires going beyond basic methods. Here’s a way to handle nested objects using lodash:

First, install lodash if you haven’t:

npm install lodash

Then, you can perform a deep merge like this:

const _ = require('lodash');

const obj1 = { key: { inner1: 5 } };
const obj2 = { key: { inner2: 7 } };

const mergedObj = _.merge({}, obj1, obj2);

console.log(mergedObj); // { key: { inner1: 5, inner2: 7 }}

This approach merges all the way down, pretty cool, right? If this helped, consider liking the post!

3

To merge nested objects in JavaScript beyond a shallow level, you need a method that goes deeper. Here’s a simple and direct way to achieve a deep merge without relying on external libraries like lodash.

Solution: Using a Custom Function

function deepMerge(target, source) {
  for (const key in source) {
    if (source[key] instanceof Object) {
      if (!target[key]) Object.assign(target, { [key]: {} });
      deepMerge(target[key], source[key]);
    } else {
      Object.assign(target, { [key]: source[key] });
    }
  }
  return target;
}

const obj1 = { key: { inner1: 5 } };
const obj2 = { key: { inner2: 7 } };

const mergedObj = deepMerge({}, obj1);
deepMerge(mergedObj, obj2);

console.log(mergedObj); // { key: { inner1: 5, inner2: 7 } }

How It Works:

  • The deepMerge function checks each property of the source object.
  • If the property is an object, it recursively merges it with the target.
  • If it’s not an object, it simply copies the value.

Benefits:

  • No external libraries needed.
  • Full control over the merging process.

This approach ensures your objects are merged as deeply as needed with a straightforward solution that avoids external dependencies.

4

Hey there! :star2: If you’re trying to merge objects in JavaScript, particularly those with nested structures, it takes a little extra magic to get it just right. Standard methods like the object spread operator don’t handle deep merges well since they only work one level deep.

If you’re into handling this without additional libraries, you can create your own deep merge function. It might look like this:

function customDeepMerge(target, source) {
  for (const key in source) {
    if (source[key] instanceof Object && !Array.isArray(source[key])) {
      if (!target[key]) Object.assign(target, { [key]: {} });
      customDeepMerge(target[key], source[key]);
    } else {
      Object.assign(target, { [key]: source[key] });
    }
  }
  return target;
}

const obj1 = { key: { inner1: 5 } };
const obj2 = { key: { inner2: 7 } };

const mergedObj = customDeepMerge({}, obj1);
customDeepMerge(mergedObj, obj2);

console.log(mergedObj); // { key: { inner1: 5, inner2: 7 } }

This method keeps everything in-house and gives you full control over how deep the merge goes. Enjoy coding! Let me know if you need more details. :blush: