facebook/react · error · Error

The `style` prop expects a mapping from style properties to

Error message

The `style` prop expects a mapping from style properties to values, not a string. For example, style={{marginRight: spacing + 'em'}} when using JSX.

What it means

Error "The `style` prop expects a mapping from style properties to values, not a string. For example, style={{marginRight: spacing + 'em'}} when using JSX." thrown in facebook/react.

Source

Thrown at packages/react-dom-bindings/src/server/ReactFizzConfigDOM.js:1273

    return chunk;
  }
  const result = stringToPrecomputedChunk(
    escapeTextForBrowser(hyphenateStyleName(styleName)),
  );
  styleNameCache.set(styleName, result);
  return result;
}

const styleAttributeStart = stringToPrecomputedChunk(' style="');
const styleAssign = stringToPrecomputedChunk(':');
const styleSeparator = stringToPrecomputedChunk(';');

function pushStyleAttribute(
  target: Array<Chunk | PrecomputedChunk>,
  style: Object,
): void {
  if (typeof style !== 'object') {
    throw new Error(
      'The `style` prop expects a mapping from style properties to values, ' +
        "not a string. For example, style={{marginRight: spacing + 'em'}} when " +
        'using JSX.',
    );
  }

  let isFirst = true;
  for (const styleName in style) {
    if (!hasOwnProperty.call(style, styleName)) {
      continue;
    }
    // If you provide unsafe user data here they can inject arbitrary CSS
    // which may be problematic (I couldn't repro this):
    // https://www.owasp.org/index.php/XSS_Filter_Evasion_Cheat_Sheet
    // http://www.thespanner.co.uk/2007/11/26/ultimate-xss-css-injection/
    // This is not an XSS hole but instead a potential CSS injection issue
    // which has lead to a greater discussion about how we're going to
    // trust URLs moving forward. See #2115901

View on GitHub (pinned to eafeac097b)

When it happens

Trigger: Thrown at packages/react-dom-bindings/src/server/ReactFizzConfigDOM.js:1273 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of facebook/react@eafeac097b (2026-08-21). Data as JSON: /api/errors/fc52dd1e4751842f. Report an issue: GitHub.