--- id: top-level-api title: Top-Level API permalink: top-level-api.html next: component-api.html redirect_from: "/docs/reference.html" --- ## React `React` is the entry point to the React library. If you're using one of the prebuilt packages it's available as a global; if you're using CommonJS modules you can `require()` it. ### React.Component ```javascript class Component ``` This is the base class for React Components when they're defined using ES6 classes. See [Reusable Components](/react/docs/reusable-components.html#es6-classes) for how to use ES6 classes with React. For what methods are actually provided by the base class, see the [Component API](/react/docs/component-api.html). ### React.createClass ```javascript ReactClass createClass(object specification) ``` Create a component class, given a specification. A component implements a `render` method which returns **one single** child. That child may have an arbitrarily deep child structure. One thing that makes components different than standard prototypal classes is that you don't need to call new on them. They are convenience wrappers that construct backing instances (via new) for you. For more information about the specification object, see [Component Specs and Lifecycle](/react/docs/component-specs.html). ### React.createElement ```javascript ReactElement createElement( string/ReactClass type, [object props], [children ...] ) ``` Create and return a new `ReactElement` of the given type. The type argument can be either an html tag name string (eg. 'div', 'span', etc), or a `ReactClass` (created via `React.createClass`). ### React.cloneElement ``` ReactElement cloneElement( ReactElement element, [object props], [children ...] ) ``` Clone and return a new `ReactElement` using `element` as the starting point. The resulting element will have the original element's props with the new props merged in shallowly. New children will replace existing children. Unlike `React.addons.cloneWithProps`, `key` and `ref` from the original element will be preserved. There is no special behavior for merging any props (unlike `cloneWithProps`). See the [v0.13 RC2 blog post](/react/blog/2015/03/03/react-v0.13-rc2.html) for additional details. ### React.createFactory ```javascript factoryFunction createFactory( string/ReactClass type ) ``` Return a function that produces ReactElements of a given type. Like `React.createElement`, the type argument can be either an html tag name string (eg. 'div', 'span', etc), or a `ReactClass`. ### React.render ```javascript ReactComponent render( ReactElement element, DOMElement container, [function callback] ) ``` Render a ReactElement into the DOM in the supplied `container` and return a reference to the component. 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. > Note: > > `React.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. > > `React.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. ### React.unmountComponentAtNode ```javascript boolean unmountComponentAtNode(DOMElement container) ``` Remove a mounted React component from the DOM and clean up its event handlers and state. If no component was mounted in the container, calling this function does nothing. Returns `true` if a component was unmounted and `false` if there was no component to unmount. ### React.renderToString ```javascript string renderToString(ReactElement element) ``` Render a ReactElement to its initial HTML. This should only be used on the server. React will return an HTML string. You can use this method to generate HTML on the server and send the markup down on the initial request for faster page loads and to allow search engines to crawl your pages for SEO purposes. If you call `React.render()` on a node that already has this server-rendered markup, React will preserve it and only attach event handlers, allowing you to have a very performant first-load experience. ### React.renderToStaticMarkup ```javascript string renderToStaticMarkup(ReactElement element) ``` Similar to `renderToString`, except this doesn't create extra DOM attributes such as `data-react-id`, that React uses internally. This is useful if you want to use React as a simple static page generator, as stripping away the extra attributes can save lots of bytes. ### React.isValidElement ```javascript boolean isValidElement(* object) ``` Verifies the object is a ReactElement. ### React.findDOMNode ```javascript DOMElement findDOMNode(ReactComponent component) ``` If this component has been mounted into the DOM, this returns the corresponding native browser DOM element. This method is useful for reading values out of the DOM, such as form field values and performing DOM measurements. When `render` returns `null` or `false`, `findDOMNode` returns `null`. ### React.DOM `React.DOM` provides convenience wrappers around `React.createElement` for DOM components. These should only be used when not using JSX. For example, `React.DOM.div(null, 'Hello World!')` ### React.PropTypes `React.PropTypes` includes types that can be used with a component's `propTypes` object to validate props being passed to your components. For more information about `propTypes`, see [Reusable Components](/react/docs/reusable-components.html). ### React.Children `React.Children` provides utilities for dealing with the `this.props.children` opaque data structure. #### React.Children.map ```javascript object React.Children.map(object children, function fn [, object thisArg]) ``` Invoke `fn` on every immediate child contained within `children` with `this` set to `thisArg`. If `children` is a nested object or array it will be traversed: `fn` will never be passed the container objects. If children is `null` or `undefined` returns `null` or `undefined` rather than an empty object. #### React.Children.forEach ```javascript React.Children.forEach(object children, function fn [, object thisArg]) ``` Like `React.Children.map()` but does not return an object. #### React.Children.count ```javascript number React.Children.count(object children) ``` Return the total number of components in `children`, equal to the number of times that a callback passed to `map` or `forEach` would be invoked. #### React.Children.only ```javascript object React.Children.only(object children) ``` Return the only child in `children`. Throws otherwise.