When developing applications with React, Next or any JavaScript Frameworks, one of the warnings you might encounter is: “Warning: Invalid DOM property. Did you mean …?” This warning indicates that a property you’ve assigned to a DOM element does not conform to the standard naming conventions used by React.
Why Does This Happen?
React uses a JavaScript-based approach to render HTML and SVG elements, requiring property names to follow JavaScript’s camelCase convention. When React encounters an attribute in the wrong format, it issues a warning to help developers correct their code and avoid potential bugs.
Example: stroke-linejoin vs. strokeLinejoin
Consider the SVG property stroke-linejoin. This property defines the shape to be used at the corners of paths or basic shapes when they are stroked. In standard HTML and SVG, this property is written in kebab-case (lowercase with hyphens)
<svg width="100" height="100"> <rect width="100" height="100" stroke="black" stroke-width="4" stroke-linejoin="round" /> </svg>
Correct Usage
<svg width="100" height="100"> <rect width="100" height="100" stroke="black" strokeWidth="4" strokeLinejoin="round" /> </svg>
Other Common Properties
Here are a few more examples of commonly used SVG attributes and their correct camelCase equivalents in React:
fill-opacity -> fillOpacity font-size -> fontSize text-anchor -> textAnchor
Conclusion
React’s warning about invalid DOM properties is a helpful reminder to use the correct camelCase naming convention for attributes. This ensures compatibility and proper functioning of your React components.