Function createContext

docs/external/js/react.development.js:1344–1450

(defaultValue, calculateChangedBits)

  }

  function createContext(defaultValue, calculateChangedBits) {
    if (calculateChangedBits === undefined) {
      calculateChangedBits = null;
    } else {
      {
        if (calculateChangedBits !== null && typeof calculateChangedBits !== 'function') {
          error('createContext: Expected the optional second argument to be a ' + 'function. Instead received: %s', calculateChangedBits);
        }
      }
    }

    var context = {
      $$typeof: REACT_CONTEXT_TYPE,
      _calculateChangedBits: calculateChangedBits,
      // As a workaround to support multiple concurrent renderers, we categorize
      // some renderers as primary and others as secondary. We only expect
      // there to be two concurrent renderers at most: React Native (primary) and
      // Fabric (secondary); React DOM (primary) and React ART (secondary).
      // Secondary renderers store their context values on separate fields.
      _currentValue: defaultValue,
      _currentValue2: defaultValue,
      // Used to track how many concurrent renderers this context currently
      // supports within in a single renderer. Such as parallel server rendering.
      _threadCount: 0,
      // These are circular
      Provider: null,
      Consumer: null
    };
    context.Provider = {
      $$typeof: REACT_PROVIDER_TYPE,
      _context: context
    };
    var hasWarnedAboutUsingNestedContextConsumers = false;
    var hasWarnedAboutUsingConsumerProvider = false;

    {
      // A separate object, but proxies back to the original context object for
      // backwards compatibility. It has a different $$typeof, so we can properly
      // warn for the incorrect usage of Context as a Consumer.
      var Consumer = {
        $$typeof: REACT_CONTEXT_TYPE,
        _context: context,
        _calculateChangedBits: context._calculateChangedBits
      }; // $FlowFixMe: Flow complains about not setting a value, which is intentional here

      Object.defineProperties(Consumer, {
        Provider: {
          get: function () {
            if (!hasWarnedAboutUsingConsumerProvider) {
              hasWarnedAboutUsingConsumerProvider = true;

              error('Rendering <Context.Consumer.Provider> is not supported and will be removed in ' + 'a future major release. Did you mean to render <Context.Provider> instead?');
            }

            return context.Provider;
          },
          set: function (_Provider) {
            context.Provider = _Provider;