Salesforce JavaScript Developer Practice Exam 2026 – Your All-in-One Guide to Exam Success!

The primary difference between a shallow copy and a deep copy of an object is that a shallow copy duplicates only the top-level properties of the object, whereas a deep copy duplicates all properties recursively. When a shallow copy is made, the new object contains references to the same nested objects as the original. This means that if the nested object is modified in the copied object, the changes will affect the original object as well, because both objects point to the same nested properties.

This understanding is crucial, especially in JavaScript, where objects are referenced by reference rather than by value. Creating a shallow copy is typically done using methods like `Object.assign()` or the spread operator (`...`), which effectively create a new object with duplicate references to the properties of the original. Consequently, any nested objects within these properties are not independently copied, contrarily to what happens with a deep copy, which creates entirely separate instances of nested properties.

Recognizing this distinction can help prevent unintended side effects in code when modifying objects, particularly when dealing with complex data structures or state management in applications.