Creating a new object with the same properties

Oct 13, 2025 by leolavanderia.com.br 7 views

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Introduction

When working with objects in Javascript, it's common to encounter situations where you need to create a copy of an object. This can be useful for a variety of reasons, such as when you want to modify the original object without affecting the copy, or when you need to preserve the original object's state. However, making a deep copy of an object in Javascript can be a bit tricky, especially when dealing with complex objects that contain nested properties.

What is a Deep Copy?

A deep copy of an object is a new object that is created by recursively traversing the original object's properties and creating new copies of each property. This means that if the original object contains nested objects or arrays, the deep copy will also contain new, independent copies of those nested objects or arrays.

Why Do We Need a Deep Copy?

Let's consider an example to illustrate the importance of making a deep copy of an object. Suppose we have an object oriObj that contains some properties, and we want to modify it without affecting the original object. However, if we simply assign a new value to oriObj, we will be modifying the original object, which may not be what we want.

const oriObj = {
  id: 1,
  version: 1,
  person: 'jack'
};
// Assign a new value to oriObj
oriObj = [];
console.log(oriObj); // Output: []
console.log(oriObj === oriObj); // Output: true (because we're modifying the original object)

As you can see, by assigning a new value to oriObj, we are modifying the original object, and the === operator returns true, indicating that the new value is the same as the original object.

How to Make a Deep Copy of an Object

To make a deep copy of an object, we can use the JSON.parse(JSON.stringify(obj)) method. This method creates a new object by parsing a JSON string that is generated from the original object.

const oriObj = {
  id: 1,
  version: 1,
  person: 'jack'
};
// Make a deep copy of oriObj
const copyObj = JSON.parse(JSON.stringify(oriObj));
console.log(copyObj); // Output:  id 1, version: 1, person: 'jack' 
console.log(copyObj === oriObj); // Output: false (because we've created a new object)

As you can see, by using JSON.parse(JSON.stringify(obj)), we've created a new object copyObj that is a deep copy of the original object oriObj.

Using Lodash's `cloneDeep` Method

Another way to make a deep copy of an object is to use Lodash's cloneDeep method. This method creates a new object by recursively traversing the original object's properties and creating new copies of each property.

const _ = require('lodash');
const oriObj = 
id 1,
version: 1,
person: 'jack'
;
// Make a deep copy of oriObj using Lodash's cloneDeep method
const copyObj = _.cloneDeep(oriObj);
console.log(copyObj); // Output:  id 1, version: 1, person: 'jack' 
console.log(copyObj === oriObj); // Output: false (because we've created a new object)

As you can see, by using Lodash's cloneDeep method, we've created a new object copyObj that is a deep copy of the original object oriObj.

Using a Custom Function to Make a Deep Copy

If you don't want to use a library like Lodash, you can also create a custom function to make a deep copy of an object. Here's an example of how you can do it:

function deepCopy(obj) {
  if (typeof obj !== 'object') {
    return obj;
  }
if (Array.isArray(obj)) {
return obj.map(deepCopy);
}
const copy = {};
for (const key in obj) {
if (Object.prototype.hasOwnProperty.call(obj, key)) {
copy[key] = deepCopy(obj[key]);
}
}
return copy;
}
const oriObj = 
id 1,
version: 1,
person: 'jack'
;
// Make a deep copy of oriObj using the custom function
const copyObj = deepCopy(oriObj);
console.log(copyObj); // Output:  id 1, version: 1, person: 'jack' 
console.log(copyObj === oriObj); // Output: false (because we've created a new object)

As you can see, by using a custom function to make a deep copy of an object, we've created a new object copyObj that is a deep copy of the original object oriObj.

Conclusion

In conclusion, making a deep copy of an object in Javascript can be a bit tricky, but there are several ways to do it. You can use the JSON.parse(JSON.stringify(obj)) method, Lodash's cloneDeep method, or create a custom function to make a deep copy of an object. By using one of these methods, you can create a new object that is a deep copy of the original object, and modify the new object without affecting the original object.

Example Use Cases

Here are some example use cases for making a deep copy of an object:

Preserving the original object's state: When you need to modify an object without affecting its original state, making a deep copy of the object can be useful.
Creating a new object with the same properties: When you need to create a new object with the same properties as an existing object, making a deep copy of the object can be useful.
Avoiding unintended modifications: When you're working with complex objects that contain nested properties, making a deep copy of the object can help you avoid unintended modifications to the original object.

Best Practices

Here are some best practices to keep in mind when making a deep copy of an object:

Use a reliable method: When making a deep copy of an object, use a reliable method such as JSON.parse(JSON.stringify(obj)) or Lodash's cloneDeep method.
Test your code: When making a deep copy of an object, test your code to ensure that it's working correctly.
Avoid using Object.assign: When making a deep copy of an object, avoid using Object.assign because it only copies the properties of the object, but not its nested properties.

Conclusion

In conclusion, making a deep copy of an object in Javascript can be a bit tricky, but there are several ways to do it. By using one of the methods mentioned in this article, you can create a new object that is a deep copy of the original object, and modify the new object without affecting the original object. Remember to use a reliable method, test your code, and avoid using Object.assign when making a deep copy of an object.

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Q: What is the difference between a shallow copy and a deep copy of an object?

A: A shallow copy of an object is a new object that contains references to the original object's properties. This means that if the original object contains nested objects or arrays, the shallow copy will also contain references to those nested objects or arrays. On the other hand, a deep copy of an object is a new object that is created by recursively traversing the original object's properties and creating new copies of each property. This means that if the original object contains nested objects or arrays, the deep copy will also contain new, independent copies of those nested objects or arrays.

Q: How do I make a deep copy of an object in Javascript?

A: There are several ways to make a deep copy of an object in Javascript. You can use the JSON.parse(JSON.stringify(obj)) method, Lodash's cloneDeep method, or create a custom function to make a deep copy of an object.

Q: What is the `JSON.parse(JSON.stringify(obj))` method?

A: The JSON.parse(JSON.stringify(obj)) method creates a new object by parsing a JSON string that is generated from the original object. This method is useful for making a deep copy of an object, but it can be slow for large objects.

Q: What is Lodash's `cloneDeep` method?

A: Lodash's cloneDeep method creates a new object by recursively traversing the original object's properties and creating new copies of each property. This method is useful for making a deep copy of an object, and it is faster than the JSON.parse(JSON.stringify(obj)) method.

Q: How do I create a custom function to make a deep copy of an object?

A: To create a custom function to make a deep copy of an object, you can use the following code:

function deepCopy(obj) {
  if (typeof obj !== 'object') {
    return obj;
  }
if (Array.isArray(obj)) {
return obj.map(deepCopy);
}
const copy = {};
for (const key in obj) {
if (Object.prototype.hasOwnProperty.call(obj, key)) {
copy[key] = deepCopy(obj[key]);
}
}
return copy;
}

Q: What are some best practices for making a deep copy of an object?

A: Here are some best practices for making a deep copy of an object:

Use a reliable method such as JSON.parse(JSON.stringify(obj)) or Lodash's cloneDeep method.
Test your code to ensure that it's working correctly.
Avoid using Object.assign because it only copies the properties of the object, but not its nested properties.

Q: What are some common use cases for making a deep copy of an object?

A: Here are some common use cases for making a deep copy of an object:

Preserving the original object's state: When you need to modify an object without affecting its original state, making a deep copy of the object can be useful.
Creating a new object with the same properties: When you need to create a new object with the same properties as an existing object, making a deep copy of the object can be useful.
Avoiding unintended modifications: When you're working with complex objects that contain nested properties, making a deep copy of the object can help you avoid unintended modifications to the original object.

Q: What are some common pitfalls to avoid when making a deep copy of an object?

A: Here are some common pitfalls to avoid when making a deep copy of an object:

Using the wrong method: Make sure to use a reliable method such as JSON.parse(JSON.stringify(obj)) or Lodash's cloneDeep method.
Not testing your code: Make sure to test your code to ensure that it's working correctly.
Using Object.assign: Avoid using Object.assign because it only copies the properties of the object, but not its nested properties.

Q: How do I troubleshoot issues with making a deep copy of an object?

A: Here are some steps you can follow to troubleshoot issues with making a deep copy of an object:

Check your code: Make sure that your code is correct and that you're using a reliable method.
Test your code: Make sure to test your code to ensure that it's working correctly.
Use a debugger: Use a debugger to step through your code and identify any issues.

Q: What are some resources for learning more about making a deep copy of an object in Javascript?

A: Here are some resources for learning more about making a deep copy of an object in Javascript:

MDN Web Docs: The MDN Web Docs have a comprehensive guide to making a deep copy of an object in Javascript.
Lodash documentation: The Lodash documentation has a section on making a deep copy of an object.
Stack Overflow: Stack Overflow has a large collection of questions and answers related to making a deep copy of an object in Javascript.