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10 Best Practices for Boolean Handling and Conditional Rendering in JSX
Follow these best practices
Prajun
May 21, 2024 • 🔖 4 minutes
When working with React and JSX, handling booleans correctly and efficiently is crucial for clean and bug-free code.
During a code review I conducted.
A developer wrote ArrayOfSomething.length && <SomeJSXFromMapFnc/> to load JSX.
The issue with this statement is that when there are items, everything works fine, and you will see components in the UI. However, if the array is empty, you will see "0" in the UI.
Conditional rendering in JSX allows you to display components or elements based on certain conditions. However, improper handling of boolean values and conditional checks can lead to unexpected behaviors and difficult-to-debug issues.
Pay careful attention to what you're checking on the left side of a logical statement, especially in JSX. Determine if the value is a string or a number, and ensure it can't be anything else.
It's a good recap to go through these tips, even if you already know them, to ensure best practices are consistently applied in your codebase.
It's a good recap to go through these tips, even if you already know them, to ensure best practices are consistently applied in your codebase.
Strings and Numbers
Always use the double bang (!!) to ensure you're working with a boolean value:
!!someString && ...
!!someNumber && ...Undefined, Null, and Zero
Avoid checking these values directly without converting them to booleans:
!!undefined && ...
!!null && ...
!!0 && ...Arrays
To check if array exists, use
Array.isArray(myArray) && ...To check if an array is not empty, ensure its length is greater than 0
myArray.length > 0 && ...
!!myArray.length && ...Objects
Avoid checking if an object exists directly. Instead, check for properties or ensure it has properties
!!obj.name && ...
Object.entries(obj).length > 0 && ... Functions
Ensure a variable is a function before invoking it
typeof someFunction === 'function' && ... Boolean Constructor
You can replace the double bang (!!) with the Boolean constructor if you prefer
Boolean(someString) && ...
Boolean(undefined) && ... Conditional Rendering
Always make sure you're working with boolean values when conditionally rendering JSX
{Boolean(condition) && <Component />} Falsy Values
Be cautious with values like 0, "" (empty string), null, undefined, and NaN since they are falsy. Explicitly convert them to booleans when necessary
!!myValue && ... Use Default Values
When dealing with optional properties or states, provide default values to avoid undefined checks
const myProp = props.myProp || 'default'; Short-Circuit Evaluation
Use short-circuit evaluation to render components conditionally without extra if-statements
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