diffHydratedProperties() — react Function Reference

Source Code

packages/react-dom-bindings/src/client/ReactDOMComponent.js lines 3265–3331

export function diffHydratedProperties(
  domElement: Element,
  tag: string,
  props: Object,
  hostContext: HostContext,
): null | Object {
  const serverDifferences: {[propName: string]: mixed} = {};
  if (__DEV__) {
    const extraAttributes: Set<string> = new Set();
    const attributes = domElement.attributes;
    for (let i = 0; i < attributes.length; i++) {
      const name = attributes[i].name.toLowerCase();
      switch (name) {
        // Controlled attributes are not validated
        // TODO: Only ignore them on controlled tags.
        case 'value':
          break;
        case 'checked':
          break;
        case 'selected':
          break;
        case 'vt-name':
        case 'vt-update':
        case 'vt-enter':
        case 'vt-exit':
        case 'vt-share':
          if (enableViewTransition) {
            // View Transition annotations are expected from the Server Runtime.
            // However, if they're also specified on the client and don't match
            // that's an error.
            break;
          }
        // Fallthrough
        default:
          // Intentionally use the original name.
          // See discussion in https://github.com/facebook/react/pull/10676.
          extraAttributes.add(attributes[i].name);
      }
    }
    if (isCustomElement(tag, props)) {
      diffHydratedCustomComponent(
        domElement,
        tag,
        props,
        hostContext,
        extraAttributes,
        serverDifferences,
      );
    } else {
      diffHydratedGenericElement(
        domElement,
        tag,
        props,
        hostContext,
        extraAttributes,
        serverDifferences,
      );
    }
    if (extraAttributes.size > 0 && props.suppressHydrationWarning !== true) {
      warnForExtraAttributes(domElement, extraAttributes, serverDifferences);
    }
  }
  if (Object.keys(serverDifferences).length === 0) {
    return null;
  }
  return serverDifferences;
}