Is it possible to pass context into a component instantiated with ReactDOM.render?

Question

TL;DR Given the following example code:

ReactDOM.render(, someDomNode);

Is it possible to manually pas

Answer 1

No. Before react 0.14 there was method React.withContext, but it was removed.

However you can do it by creating HoC component with context, it would be something like:

import React from 'react';

function createContextProvider(context){
  class ContextProvider extends React.Component {
    getChildContext() {
      return context;
    }

    render() {
      return this.props.children;
    }
  }

  ContextProvider.childContextTypes = {};
  Object.keys(context).forEach(key => {
    ContextProvider.childContextTypes[key] = React.PropTypes.any.isRequired; 
  });

  return ContextProvider;
}

And use it as following:

const ContextProvider = createContextProvider(context);

ReactDOM.render(
  <ContextProvider>
    <MyComponent prop1={someVar} />
  </ContextProvider>,
  someDomNode
);

Answer 2

In React 15 and earlier you can use ReactDOM.unstable_renderSubtreeIntoContainer instead of ReactDOM.render. The first argument is the component who's context you want to propagate (generally this)

In React 16 and later there's the "Portal" API: https://reactjs.org/docs/portals.html