When Should I Use Nullish Coalescing Vs Logical Or

Nullish coalescing and logical OR operators are essential tools in a developer's arsenal when writing code in languages like JavaScript. Understanding when to use each can greatly improve the readability and performance of your code.

Let's break it down in a straightforward way. The Nullish coalescing operator (??) returns the right-hand operand when the left-hand operand is null or undefined. On the other hand, the logical OR operator (||) returns the first truthy value it encounters. So, when should you choose one over the other?

### Nullish Coalescing Operator (??)
Use the Nullish coalescing operator when you specifically want to check for null or undefined values. For instance, consider a scenario where you have a variable that might be null, and you want to provide a default value in case of null or undefined.

const myVariable = null;
const result = myVariable ?? 'Default Value';
console.log(result); // Output: Default Value

In this case, the variable `result` will be assigned the value 'Default Value' because `myVariable` is null.

### Logical OR Operator (||)
The logical OR operator, on the other hand, is more generic and checks for any falsy value. This means it will return the right-hand operand if the left-hand operand is falsy, not just null or undefined. It is commonly used to set default values for variables that might be falsy.

const myValue = 0;
const result = myValue || 'Default Value';
console.log(result); // Output: Default Value

Here, the variable `result` will be 'Default Value' because `myValue` is 0, which is considered falsy.

### Choosing Between the Two
If you want to ensure that only null or undefined values trigger the default assignment, go for the Nullish coalescing operator. This operator helps make your intentions clear and prevents unexpected behavior in scenarios where falsy values other than null or undefined are present.

On the other hand, if you are okay with any falsy value triggering the default assignment, the logical OR operator is a more flexible choice.

### Performance Considerations
In terms of performance, the Nullish coalescing operator is more precise in its checks, specifically targeting null and undefined values. This can be beneficial for scenarios where you only care about null or undefined, as it avoids triggering the default assignment for other falsy values.

The logical OR operator, being more generalized, might be slightly faster since it checks for a broader range of falsy values. However, the difference in performance is negligible unless you are working on highly optimized code where every microsecond counts.

In conclusion, understanding the differences between the Nullish coalescing and logical OR operators allows you to write more robust and predictable code. Choose the operator that best suits your specific use case to enhance the clarity and reliability of your JavaScript code.