When working with JavaScript, you may come across situations where you need to add a new key to a const object. While const ensures that the variable itself cannot be reassigned, it does not prevent modifications to the object's properties. Therefore, it is possible to add new keys to a const object without violating its immutability. Here are a few techniques to achieve this:
1. Using Object.assign:
Object.assign can be used to create a new object by merging the properties of existing objects. By creating a new object with the additional key and merging it with the original object, you can effectively add a new key to a const object.
```javascript
const originalObject = { key1: 'value1' };
const newKey = 'key2';
const valueForNewKey = 'value2';
const updatedObject = Object.assign({}, originalObject, { [newKey]: valueForNewKey });
```
2. Using the spread operator:
The spread operator (...) can also be used to create a new object with the additional key. By spreading the properties of the original object and adding the new key-value pair, a new object with the updated properties can be created.
```javascript
const originalObject = { key1: 'value1' };
const newKey = 'key2';
const valueForNewKey = 'value2';
const updatedObject = { ...originalObject, [newKey]: valueForNewKey };
```
3. Using Object.defineProperty:
Object.defineProperty allows you to add a new property to an object, or modify an existing one, with a specified configuration. This method allows for fine-grained control over the added property.
```javascript
const originalObject = { key1: 'value1' };
const newKey = 'key2';
const valueForNewKey = 'value2';
Object.defineProperty(originalObject, newKey, {
value: valueForNewKey,
writable: true,
enumerable: true,
configurable: true
});
```
These techniques provide different ways to add new keys to a const object in JavaScript without violating its immutability. They allow you to work with const objects while still being able to update and modify their properties as needed.