Shallow copy and Deep copy in JavaScript

Introduction:

Have you ever needed to create a copy of an object or array in your JavaScript code? If so, you might have come across two types of copy operations: shallow copy and deep copy. Shallow copy and deep copy are used to create copies of objects and arrays in JavaScript, but they differ in how they copy the data. In this post, we'll explore the differences between shallow copy and deep copy and when to use each type of copy operation. By the end of this post, you'll have a better understanding of these copy operations and be able to make an informed decision on which one to use in your own code.

Shallow copy and deep copy are two types of copy operations used in JavaScript to create copies of objects and arrays. While both types of copy serve the same purpose of creating a copy of an object or array, they differ in how they copy the data.

Shallow copy:

A shallow copy is a type of copy operation that creates a new object or array with the same values as the original. However, if the original object or array contains other objects or arrays nested within it, the shallow copy only copies the reference to the nested object or array, not the object or array itself. This means that any changes made to the nested object or array will affect both the original object and its shallow copy.

To perform a shallow copy in JavaScript, you can use the spread operator, Object.assign(), or Array.slice(). For example:

const original = {a: 1, b: {c: 2}};
const shallowCopy = {...original}; // or Object.assign({}, original) or original.slice()

Deep Copy:

A deep copy, on the other hand, is a type of copy operation that creates a new object or array and recursively copies all properties of the original object and its nested objects or arrays. This ensures that all nested objects or arrays are also copied, and any changes made to the nested object or array will not affect the original object or its deep copy.

To perform a deep copy in JavaScript, you can use methods like JSON.stringify() and JSON.parse(), custom recursive functions, or third-party libraries like lodash or Immutable.js. For example:

const original = {a: 1, b: {c: 2}};
const deepCopy = JSON.parse(JSON.stringify(original)); // or use a custom recursive function or a library like lodash

When to use shallow copy or deep copy in JavaScript depends on the specific requirements of your code. Shallow copy is usually faster and simpler than deep copy and is suitable for simple objects or arrays without any nested objects or arrays. Deep copy, on the other hand, is more thorough and is suitable for complex objects or arrays with nested objects or arrays.

Conclusion:

In conclusion, shallow copy and deep copy are both useful copy operations in JavaScript, and choosing the right one depends on your specific use case. Understanding the differences between the two can help you create more efficient and reliable code.