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

• [x] Headings (1 to 6)
• [x] Paragraph
• [x] Emphasis (bold, italic, and strikethrough)
• [x] Link
• [x] Image
• [x] Blockquote
• [x] Inline Code
• [x] Code Block
• [x] List (ordered, unordered)
• [x] Horizontal Rule
• [x] 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, 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 {
    const text = args?.text as string;
    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