How to fix the 'Received "true" for a non-boolean attribute' error

If you use styled-components, you maybe encountered the following error.

Warning: Received "true" for a non-boolean attribute

There is an official solution that you can find here. I'll present an alternative to this solution.

The trick is to use the unary plus operator to convert boolean to number.

// Convert boolean to numbers
+true; // 1
+false; // 0

// Conditions are still valid using 0 and 1
0 ? "jean" : "smaug"; // smaug
1 ? "jean" : "smaug"; // jean

In order to make a real world example, we'll style the Link component from react-router.

import styled from "styled-components";
import { Link } from "react-router";

const StyledLink = styled(Link)`
  color: ${({ inverted }) => (inverted ? "white" : "chartreuse")};
`;

function Navbar() {
  return (
    <nav>
      {# Bad #}
      <StyledLink inverted={true}>Home</StyledLink>

      {# Good #}
      <StyledLink inverted={+true}>About</StyledLink>
    </nav>
  );
}

Fixing this error is very simple. You just need to add + before your booleans values. According to MDN unary operator is the preferred way for number conversion.

You can find the banner image here.

Thanks for reading.

Maxime Blanc


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