ReactJS Tips & Tricks: Avoid Short-Circuit Conditional UI Rendering

The goal of this articles is to share with you some insights that I have learned
over the last few years that I have been working with ReactJS.

I will start with a common one that is called Short-Circuit Conditional unexpected UI rendering.

What is a Short-Circuit conditional?

This conditional is a concise way to render UI components.

Example of the Short-Circuit conditional approach:

const Component = ({ number = 0 }) => number && <div>Current: {number}</div>

The component I mentioned before will backfire a 0.

Why does it render zero instead of the empty UI?

The comparison operators in JavaScript don't return boolean values, they return one of the compared values.

In the case mentioned above, when we check the number value it will render zero.

How to avoid the unexpected UI rendering

The way to avoid this issue is using the ternary comparison to be explicit about what will return in both scenarios.

Fixing the Component using the ternary comparison such as:

const Component = ({ number = 0 }) => (number ? <div>Current: {number}</div> : null)

Considering the value of number variable is zero, it will return null that is the second option from the ternary on this case React won't render because it is a null value.

Wrapping Up

If you think this series of articles is helpful to you, or do you want to discuss some programming topics, feel free to reach out to me at @helderburato.

Thanks! ⚡️

Comments

[Omar Benmegdoul]

Just use !!number

[Helder Berto]

You can do that, but personally, I think the ternary is more explicit in that case, and you avoid to do a value conversion before render.

[vladi160]

I am not sure you can return null for JSX, try with '' or <></>

[Mike Robinson]

Yes @vladi160 , you can return null in JSX.

[Maciek Grzybek]

You can 💯 :)