setValueForStyles() — react Function Reference

Source Code

packages/react-dom-bindings/src/client/CSSPropertyOperations.js lines 111–166

export function setValueForStyles(node, styles, prevStyles) {
  if (styles != null && typeof styles !== '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.',
    );
  }
  if (__DEV__) {
    if (styles) {
      // Freeze the next style object so that we can assume it won't be
      // mutated. We have already warned for this in the past.
      Object.freeze(styles);
    }
  }

  const style = node.style;

  if (prevStyles != null) {
    if (__DEV__) {
      validateShorthandPropertyCollisionInDev(prevStyles, styles);
    }

    for (const styleName in prevStyles) {
      if (
        prevStyles.hasOwnProperty(styleName) &&
        (styles == null || !styles.hasOwnProperty(styleName))
      ) {
        // Clear style
        const isCustomProperty = styleName.indexOf('--') === 0;
        if (isCustomProperty) {
          style.setProperty(styleName, '');
        } else if (styleName === 'float') {
          style.cssFloat = '';
        } else {
          style[styleName] = '';
        }
        trackHostMutation();
      }
    }
    for (const styleName in styles) {
      const value = styles[styleName];
      if (styles.hasOwnProperty(styleName) && prevStyles[styleName] !== value) {
        setValueForStyle(style, styleName, value);
        trackHostMutation();
      }
    }
  } else {
    for (const styleName in styles) {
      if (styles.hasOwnProperty(styleName)) {
        const value = styles[styleName];
        setValueForStyle(style, styleName, value);
      }
    }
  }
}