ReactDOM.render

ReactDOM.render

render(
  ReactElement element,
  DOMElement container,
  [function callback]
)

Render a ReactElement into the DOM in the supplied container and return a reference to the component (or returns null for stateless components).

If the ReactElement was previously rendered into container, this will perform an update on it and only mutate the DOM as necessary to reflect the latest React component.

If the optional callback is provided, it will be executed after the component is rendered or updated.

ReactDOM.render() controls the contents of the container node you pass in. Any existing DOM elements inside are replaced when first called. Later calls use React’s DOM diffing algorithm for efficient updates.

ReactDOM.render() does not modify the container node (only modifies the children of the container). In the future, it may be possible to insert a component to an existing DOM node without overwriting the existing children.

ReactDOM.render() currently returns a reference to the root ReactComponent instance. However, using this return value is legacy and should be avoided because future versions of React may render components asynchronously in some cases. If you need a reference to the root ReactComponent instance, the preferred solution is to attach a callback ref to the root element.