@jeongshin/react-native-marked

react-native-marked

Markdown renderer for React Native powered by marked.js with built-in theming support

Installation

yarn add react-native-marked react-native-svg

Usage

Using Component

import * as React from "react";
import Markdown from "react-native-marked";

const ExampleComponent = () => {
  return (
    <Markdown
      value={`# Hello world`}
      flatListProps={{
        initialNumToRender: 8,
      }}
    />
  );
};

export default ExampleComponent;

Props

Prop	Description	Type	Optional?
value	Markdown value	string	false
flatListProps	Props for customizing the underlying FlatList used	Omit<FlatListProps<ReactNode>, 'data' | 'renderItem' | 'horizontal'> ('data', 'renderItem', and 'horizontal' props are omitted and cannot be overridden.)	true
styles	Styles for parsed components	MarkedStyles	true
theme	Props for customizing colors and spacing for all components,and it will get overridden with custom component style applied via 'styles' prop	UserTheme	true
baseUrl	A prefix url for any relative link	string	true
renderer	Custom component Renderer	RendererInterface	true

Using hook

useMarkdown hook will return list of elements that can be rendered using a list component of your choice.

import React, { Fragment } from "react";
import { ScrollView, useColorScheme } from "react-native";
import { useMarkdown, type useMarkdownHookOptions } from "react-native-marked";

const CustomComponent = () => {
  const colorScheme = useColorScheme();
  const options: useMarkdownHookOptions = {
    colorScheme
  }
  const elements = useMarkdown("# Hello world", options);
  return (
    <ScrollView>
      {elements.map((element, index) => {
        return <Fragment key={`demo_${index}`}>{element}</Fragment>
      })}
    </ScrollView>
  );
};

Options

Option	Description	Type	Optional?
colorScheme	Device color scheme ("dark" or "light")	ColorSchemeName	false
styles	Styles for parsed components	MarkedStyles	true
theme	Props for customizing colors and spacing for all components,and it will get overridden with custom component style applied via 'styles' prop	UserTheme	true
baseUrl	A prefix url for any relative link	string	true
renderer	Custom component Renderer	RendererInterface	true
tokenizer	Generate custom tokens	MarkedTokenizer	true

Examples

• RN App: https://github.com/gmsgowtham/react-native-marked-test
• CodeSandbox: https://codesandbox.io/s/react-native-marked-l2hpi3?file=/src/App.js

Supported elements

• Headings (1 to 6)
• Paragraph
• Emphasis (bold, italic, and strikethrough)
• Link
• Image
• Blockquote
• Inline Code
• Code Block
• List (ordered, unordered)
• Horizontal Rule
• Table
• HTML

Ref: CommonMark

HTML will be treated as plain text. Please refer issue#290 for a potential solution

Advanced

Using custom components

Custom components can be used to override elements, i.e. Code Highlighting, Fast Image integration

Example

import React, { ReactNode, Fragment } from "react";
import { Text, ScrollView } from "react-native";
import type { ImageStyle, TextStyle } from "react-native";
import Markdown, { Renderer, useMarkdown } from "react-native-marked";
import type { RendererInterface } from "react-native-marked";
import FastImage from "react-native-fast-image";

class CustomRenderer extends Renderer implements RendererInterface {
  constructor() {
    super();
  }

  codespan(text: string, _styles?: TextStyle): ReactNode {
    return (
      <Text key={this.getKey()} style={{ backgroundColor: "#ff0000" }}>
        {text}
      </Text>
    );
  }

  image(uri: string, _alt?: string, _style?: ImageStyle): ReactNode {
    return (
      <FastImage
        key={this.getKey()}
        style={{ width: 200, height: 200 }}
        source={{ uri: uri }}
        resizeMode={FastImage.resizeMode.contain}
      />
    );
  }
}

const renderer = new CustomRenderer();

const ExampleComponent = () => {
  return (
    <Markdown
      value={"`Hello world`"}
      flatListProps={{
        initialNumToRender: 8,
      }}
      renderer={renderer}
    />
  );
};

// Alternate using hook
const ExampleComponentWithHook = () => {
  const elements = useMarkdown("`Hello world`", { renderer });

  return (
    <ScrollView>
      {elements.map((element, index) => {
        return <Fragment key={`demo_${index}`}>{element}</Fragment>
      })}
    </ScrollView>
  )
}

export default ExampleComponent;

Please refer to RendererInterface for all the overrides

Note:

For key property for a component, you can use the getKey method from Renderer class.

Using tokenizer with custom components

Refer marked

The tokenizer defines how to turn markdown text into tokens. If you supply a tokenizer object to the Marked options, it will be merged with the built-in tokenizer and any functions inside will override the default handling of that token type.

---

The implementation requires you to return a token of type 'custom' (ref: CustomToken) and the same needs to be implemented in the Renderer

Example

Overriding default codespan tokenizer to include LaTeX.

import React, { ReactNode } from "react";
import Markdown, { Renderer, MarkedTokenizer, MarkedLexer } from "react-native-marked";
import type { RendererInterface, type CustomToken, } from "react-native-marked";

class CustomTokenizer extends MarkedTokenizer<CustomToken> {
  // Override
  codespan(this: MarkedTokenizer<CustomToken>, src: string) {
    const match = src.match(/^\$+([^\$\n]+?)\$+/);
    if (match?.[1]) {
      const text = match[1].trim();
      const token: CustomToken = {
        type: 'custom',
        raw: match[0], // should be the exact regex pattern match
        identifier: "latex", // Uniq identifier for the token
        tokens: MarkedLexer(text), // optional, can be used if the markdown contains children
        args: { // optional, can be used to send more information to the renderer
          text: text,
        }
      };
      return token;
    }

    return super.codespan(src)
  }
}

class CustomRenderer extends Renderer implements RendererInterface {
  // Custom Token implementation
  custom(identifier: string, _raw: string, _children?: ReactNode[], args?: Record<string, unknown>): ReactNode {
    if (identifier === "latex") {
      const styles = {
        padding: 16,
        minWidth: "100%",
        backgroundColor: "#f6f8fa"
      };
      return this.code(text.trim(), "latex", styles);
    }
    return null;
  }
}

const renderer = new CustomRenderer();
const tokenizer = new CustomTokenizer();

const ExampleComponent = () => {
  return (
    <Markdown
      value={"$ latex code $\n\n` other code `"}
      flatListProps={{
        initialNumToRender: 8,
      }}
      renderer={renderer}
      tokenizer={tokenizer}
    />
  );
};

Example

Screenshots

Dark Theme	Light Theme

Contributing

See the contributing guide to learn how to contribute to the repository and the development workflow.

License

MIT

---

Made with create-react-native-library

Built using

• Marked

• @jsamr/react-native-li

• react-native-table-component

• react-native-svg

• svg-parser