react/packages/react-dom-bindings/src/shared/isCustomElement.js

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */

function isCustomElement(tagName: string, props: Object): boolean {
  if (tagName.indexOf('-') === -1) {
    return false;
  }
  switch (tagName) {
    // These are reserved SVG and MathML elements.
    // We don't mind this list too much because we expect it to never grow.
    // The alternative is to track the namespace in a few places which is convoluted.
    // https://html.spec.whatwg.org/multipage/custom-elements.html#custom-elements-core-concepts
    case 'annotation-xml':
    case 'color-profile':
    case 'font-face':
    case 'font-face-src':
    case 'font-face-uri':
    case 'font-face-format':
    case 'font-face-name':
    case 'missing-glyph':
      return false;
    default:
      return true;
  }
}

export default isCustomElement;