The react-is package is a collection of utilities that allow you to determine the type of a React element. It is useful for type-checking elements and for working with React's different types of components and elements in a more abstract way.

What are react-is's main functionalities?

Type-checking elements

This feature allows you to check if a value is a valid React component type or a React element. It's useful for validating props or for conditional rendering logic.

import { isValidElementType, isElement } from 'react-is';

const MyComponent = () => <div>Hello World</div>;
const myElement = <MyComponent />;

const validType = isValidElementType(MyComponent); // true
const elementCheck = isElement(myElement); // true

Identifying different element types

This feature allows you to identify specific element types like fragments, strict mode wrappers, and portals. This can be useful when writing custom rendering logic or testing components.

import { isFragment, isStrictMode, isPortal } from 'react-is';

const myFragment = <React.Fragment></React.Fragment>;
const myStrictMode = <React.StrictMode></React.StrictMode>;
const myPortal = ReactDOM.createPortal(<div />, document.body);

const fragmentCheck = isFragment(myFragment); // true
const strictModeCheck = isStrictMode(myStrictMode); // true
const portalCheck = isPortal(myPortal); // true

Working with Context

This feature allows you to check if an element is a Context Provider or a Context Consumer. This is particularly useful in higher-order components or in libraries that need to handle context-related elements.

import { isContextConsumer, isContextProvider } from 'react-is';

const MyContext = React.createContext();

const contextProviderCheck = isContextProvider(<MyContext.Provider value={null}></MyContext.Provider>); // true
const contextConsumerCheck = isContextConsumer(<MyContext.Consumer>{() => null}</MyContext.Consumer>); // true

Other packages similar to react-is

Changelog

Source

18.1.0 (April 26, 2022)

React DOM

Fix the false positive warning about react-dom/client when using UMD bundle. (@alireza-molaee in #24274)
Fix suppressHydrationWarning to work in production too. (@gaearon in #24271)
Fix componentWillUnmount firing twice inside of Suspense. (@acdlite in #24308)
Fix some transition updates being ignored. (@acdlite in #24353)
Fix useDeferredValue causing an infinite loop when passed an unmemoized value. (@acdlite in #24247)
Fix throttling of revealing Suspense fallbacks. (@sunderls in #24253)
Fix an inconsistency in whether the props object is the same between renders. (@Andarist and @acdlite in #24421)
Fix a missing warning about a setState loop in useEffect. (@gaearon in #24298)
Fix a spurious hydration error. (@gnoff in #24404)
Warn when calling setState in useInsertionEffect. (@gaearon in #24295)
Ensure the reason for hydration errors is always displayed. (@gaearon in #24276)

React DOM Server

Fix escaping for the bootstrapScriptContent contents. (@gnoff in #24385)
Significantly improve performance of renderToPipeableStream. (@gnoff in #24291)

ESLint Plugin: React Hooks

Fix false positive errors with a large number of branches. (@scyron6 in #24287)
Don't consider a known dependency stable when the variable is reassigned. (@afzalsayed96 in #24343)

Use Subscription

Replace the implementation with the use-sync-external-store shim. (@gaearon in #24289)

Readme

Source

`react-is`

This package allows you to test arbitrary values and see if they're a particular React element type.

Installation

# Yarn
yarn add react-is

# NPM
npm install react-is

Usage

Determining if a Component is Valid

import React from "react";
import * as ReactIs from "react-is";

class ClassComponent extends React.Component {
  render() {
    return React.createElement("div");
  }
}

const FunctionComponent = () => React.createElement("div");

const ForwardRefComponent = React.forwardRef((props, ref) =>
  React.createElement(Component, { forwardedRef: ref, ...props })
);

const Context = React.createContext(false);

ReactIs.isValidElementType("div"); // true
ReactIs.isValidElementType(ClassComponent); // true
ReactIs.isValidElementType(FunctionComponent); // true
ReactIs.isValidElementType(ForwardRefComponent); // true
ReactIs.isValidElementType(Context.Provider); // true
ReactIs.isValidElementType(Context.Consumer); // true
ReactIs.isValidElementType(React.createFactory("div")); // true

Determining an Element's Type

Context

import React from "react";
import * as ReactIs from 'react-is';

const ThemeContext = React.createContext("blue");

ReactIs.isContextConsumer(<ThemeContext.Consumer />); // true
ReactIs.isContextProvider(<ThemeContext.Provider />); // true
ReactIs.typeOf(<ThemeContext.Provider />) === ReactIs.ContextProvider; // true
ReactIs.typeOf(<ThemeContext.Consumer />) === ReactIs.ContextConsumer; // true

Element

import React from "react";
import * as ReactIs from 'react-is';

ReactIs.isElement(<div />); // true
ReactIs.typeOf(<div />) === ReactIs.Element; // true

Fragment

import React from "react";
import * as ReactIs from 'react-is';

ReactIs.isFragment(<></>); // true
ReactIs.typeOf(<></>) === ReactIs.Fragment; // true

Portal

import React from "react";
import ReactDOM from "react-dom";
import * as ReactIs from 'react-is';

const div = document.createElement("div");
const portal = ReactDOM.createPortal(<div />, div);

ReactIs.isPortal(portal); // true
ReactIs.typeOf(portal) === ReactIs.Portal; // true

StrictMode

import React from "react";
import * as ReactIs from 'react-is';

ReactIs.isStrictMode(<React.StrictMode />); // true
ReactIs.typeOf(<React.StrictMode />) === ReactIs.StrictMode; // true

Keywords

react

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Last updated on 26 Apr 2022

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react-is