How to copy an object in javascript

JavaScript is a powerful programming language that provides many methods to manipulate objects. In JavaScript, an object refers to a data structure consisting of key-value pairs. Sometimes we need to copy an object instead of simply referencing it. In this article, we will discuss the different ways of copying objects in JavaScript.

Method 1: Use Object.assign()

Use the Object.assign() method to copy all properties of one or more source objects to the target object. This method can also be used to copy objects.

For example, we have an object containing employee information:

let employee = {
    name: 'John Doe',
    age: 25,
    position: 'Developer'
};

We can use Object.assign() to copy this object:

let newEmployee = Object.assign({}, employee);

In this example, we Use an empty object as the target object and pass it as the first argument. The source object (employee) is the second parameter. When we run this code, a new object newEmployee will be created containing all the properties and values ​​of the employee object.

If we want to copy multiple objects, we can pass them to the Object.assign() method in order, as shown below:

let newEmployee = Object.assign({}, employee1, employee2, employee3);

Method 2: Use the spread operator

The spread operator (...) was introduced in ES6, which can be used in different places. We can use spread operator in an array or object to spread its elements. Use the spread operator in an object to copy all properties from the source object to the target object.

For example, we can use the spread operator to copy the employee object:

let newEmployee = { ...employee };

In this example, we use all the properties expanded from the employee object to create a new object newEmployee. The "..." here is the syntax of the spread operator. It extracts all properties from employee object and adds them to new object newEmployee. This new object is a completely independent object and not a reference to the employee object.

Method 3: Use JSON.parse() and JSON.stringify()

In JavaScript, we can also use the JSON.parse() and JSON.stringify() methods to copy an object . We can convert the object to a JSON string and then parse the string into a new object.

For example, we have an object:

let employee = {
    name: 'John Doe',
    age: 25,
    position: 'Developer'
};

We can use the JSON.parse() and JSON.stringify() methods to copy this object:

let newEmployee = JSON.parse(JSON.stringify(employee));

These two Combinations of methods can be very useful in copying objects. However, be aware that it may not copy special data types that contain functions, object references, or cannot be converted to JSON strings.

Method 4: Use the deep copy method

If none of the above methods can meet your requirements, you can use the deep copy method. The deep copy method copies the entire object, including object references and sub-objects. There are many libraries that provide deep copy methods, such as Lodash, Underscore.js, etc. Here we will introduce using the Lodash library to copy an object.

First, you need to install the Lodash library. In Node.js, you can use the following command to install:

npm install lodash

In the browser, you can use the following CDN link:

<script src="https://cdn.jsdelivr.net/lodash/4.17.15/lodash.min.js"></script>

After installing and introducing the Lodash library, you can Use the cloneDeep() method to create a copy of the original object:

let newObject = _.cloneDeep(originalObject);

In this example, the cloneDeep() method will completely copy the originalObject object and then return the new object newObject.

Conclusion

The above are the different ways to copy objects in JavaScript. Each method has its pros and cons, depending on your needs. Before using these methods, it is important to understand how each method works and determine which one is best for your specific situation. Whichever method you choose, make sure you understand when you are copying an object reference and when you are copying the object itself.

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