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Helder Berto
Helder Berto

Posted on • Updated on • Originally published at

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>
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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)
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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! ⚡️

Top comments (5)

omarbenmegdoul profile image
Omar Benmegdoul

Just use !!number

helderberto profile image
Helder Berto • Edited

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 profile image

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

multiwebinc profile image
Mike Robinson

Yes @vladi160 , you can return null in JSX.

maciekgrzybek profile image
Maciek Grzybek

You can 💯 :)